[Nexus 6P Q&A, Help & Troubleshooting] ceribik:
I've had the same issue since I got the phone. It happens once every week or two on average, and it results in the phone freezing for 20-30 seconds, followed by a restart. It almost always occurs when I'm interacting with the phone (most often when scrolling in a reddit app), but it has happened once or twice overnight.

I suspect it is a hardware issue as I don't believe that userspace apps should be able to cause this (or at least, they ought not to be able to crash the phone...) and I've heard of other people with the same issues uncommonly.

Can you check your phone's date of manufacture? You can do this by going into fastboot and selecting the barcodes menu option.

Here are some interesting last_kmsg logs from the last two events:

(missing preceeding logs due to log spam)
[84739.791974]lowmemorykiller: Killing 'android:ui' (18518), adj 906,
[84739.791974] to free 66740kB on behalf of 'kswapd0' (135) because
[84739.791974] cache 316852kB is below limit 322560kB for oom_score_adj 906
[84739.791974] Free memory is 11064kB above reserved
[84739.907688] lowmemorykiller: Killing 'ackageinstaller' (18478), adj 906,
[84739.907688] to free 49900kB on behalf of 'kswapd0' (135) because
[84739.907688] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.907688] Free memory is 60508kB above reserved
[84739.908238] lowmemorykiller: Killing 'Jit thread pool' (18481), adj 906,
[84739.908238] to free 49952kB on behalf of 'kswapd0' (135) because
[84739.908238] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.908238] Free memory is 60508kB above reserved
[84739.908348] lowmemorykiller: Killing 'FinalizerDaemon' (18486), adj 906,
[84739.908348] to free 50040kB on behalf of 'kswapd0' (135) because
[84739.908348] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.908348] Free memory is 60508kB above reserved
[84739.908492] lowmemorykiller: Killing 'HeapTaskDaemon' (18488), adj 906,
[84739.908492] to free 50224kB on behalf of 'kswapd0' (135) because
[84739.908492] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.908492] Free memory is 60508kB above reserved
[84739.908977] lowmemorykiller: Killing ':UploadToFolder' (18533), adj 906,
[84739.908977] to free 37892kB on behalf of 'kswapd0' (135) because
[84739.908977] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.908977] Free memory is 60508kB above reserved
[84739.909298] lowmemorykiller: Killing 'Jit thread pool' (18538), adj 906,
[84739.909298] to free 37984kB on behalf of 'kswapd0' (135) because
[84739.909298] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.909298] Free memory is 60508kB above reserved
[84739.909379] lowmemorykiller: Killing 'FinalizerDaemon' (18541), adj 906,
[84739.909379] to free 38100kB on behalf of 'kswapd0' (135) because
[84739.909379] cache 289696kB is below limit 322560kB for oom_score_adj 906
[84739.909379] Free memory is 60508kB above reserved

[74660.445598] i2c-msm-v2 f9923000.i2c: NACK: slave not responding, ensure its powered: msgs(n:1 cur:0 tx) bc(rx:0 tx:10) mode:FIFO slv_addr:0x28 MSTR_STS:0x0d1300c8 OPER:0x00000090
[74660.527433] type=1400 audit(1499172819.129:2262): avc: denied { search } for pid=8882 comm=2048616E646C657220546872656164 name="leds" dev="sysfs" ino=12900 scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:sysfs_led:s0 tclass=dir permissive=0
[74665.643519] type=1400 audit(1499172824.245:2263): avc: denied { search } for pid=8882 comm=2048616E646C657220546872656164 name="leds" dev="sysfs" ino=12900 scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:sysfs_led:s0 tclass=dir permissive=0
[74716.850927] healthd: battery l=59 v=3854 t=24.7 h=2 st=3 c=-281 chg=
[74776.912258] healthd: battery l=59 v=3856 t=25.0 h=2 st=3 c=-276 chg=
[74777.585513] healthd: battery l=59 v=3856 t=25.0 h=2 st=3 c=-276 chg=
[74817.010491]lowmemorykiller: Killing 'ogle.android.gm' (18102), adj 906,
[74817.010491] to free 65452kB on behalf of 'kswapd0' (135) because
[74817.010491] cache 319616kB is below limit 322560kB for oom_score_adj 906
[74817.010491] Free memory is -1968kB above reserved
[74817.011215] lowmemorykiller: Killing 'FinalizerWatchd' (18111), adj 906,
[74817.011215] to free 65660kB on behalf of 'kswapd0' (135) because
[74817.011215] cache 319324kB is below limit 322560kB for oom_score_adj 906
[74817.011215] Free memory is -1772kB above reserved
[74817.012017] lowmemorykiller: Killing 'e.process.gapps' (8732), adj 906,
[74817.012017] to free 37172kB on behalf of 'kswapd0' (135) because
[74817.012017] cache 319032kB is below limit 322560kB for oom_score_adj 906
[74817.012017] Free memory is -1576kB above reserved
[74817.015941] lowmemorykiller: Killing 'ndroid.settings' (18552), adj 906,
[74817.015941] to free 34912kB on behalf of 'kswapd0' (135) because
[74817.015941] cache 318448kB is below limit 322560kB for oom_score_adj 906
[74817.015941] Free memory is -988kB above reserved
[74817.019351] lowmemorykiller: Killing 'droid.apps.plus' (14639), adj 906,
[74817.019351] to free 31976kB on behalf of 'kswapd0' (135) because
[74817.019351] cache 317280kB is below limit 322560kB for oom_score_adj 906
[74817.019351] Free memory is 332kB above reserved
[74817.079463] binder: 8732: binder_alloc_buf, no vma
[74825.687222] SMBCHG: smbchg_external_power_changed: smbchg_external_power_changed: current_limit = 0
[74825.688381] healthd: battery l=58 v=3756 t=25.5 h=2 st=3 c=-895 chg=
[74825.691287] healthd: battery l=58 v=3756 t=25.5 h=2 st=3 c=-895 chg=
[74885.755321] healthd: battery l=58 v=3872 t=26.0 h=2 st=3 c=-135 chg=
[74920.211282] ETHER_TYPE_802_1X [RX]: ver 2, type 3, replay 43
[74920.218014] ETHER_TYPE_802_1X [TX]: ver 1, type 3, replay 43
[74945.819838] healthd: battery l=58 v=3874 t=26.5 h=2 st=3 c=-146 chg=
[75005.881346] healthd: battery l=57 v=3859 t=27.2 h=2 st=3 c=-167 chg=
[75053.911140] lowmemorykiller: Killing 'com.groupon' (14554), adj 906,
[75053.911140] to free 63388kB on behalf of 'kswapd0' (135) because
[75053.911140] cache 320304kB is below limit 322560kB for oom_score_adj 906
[75053.911140] Free memory is 5028kB above reserved
[75053.911919] lowmemorykiller: Killing 'Signal Catcher' (14561), adj 906,
[75053.911919] to free 63436kB on behalf of 'kswapd0' (135) because
[75053.911919] cache 320304kB is below limit 322560kB for oom_score_adj 906
[75053.911919] Free memory is 5028kB above reserved
[75062.511529] QSEECOM: qseecom_load_app: App (widevine) does'nt exist, loading apps for first time
[75062.529198] QSEECOM: qseecom_load_app: App with id 186 (widevine) now loaded
[75062.661885] QSEECOM: qseecom_unload_app: App id 186 now unloaded
[75063.317888] type=1400 audit(1499173221.919:2264): avc: denied { read } for pid=19764 comm="Binder:19752_2" name="address" dev="sysfs" ino=23761 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:sysfs_mac_address:s0 tclass=file permissive=0
[75063.329706] type=1400 audit(1499173221.926:2265): avc: denied { read } for pid=19764 comm="Binder:19752_2" name="/" dev="tmpfs" ino=5436 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:device:s0 tclass=dir permissive=0
[75065.942980] healthd: battery l=57 v=3868 t=28.0 h=2 st=3 c=-130 chg=
[75066.149548] QSEECOM: qseecom_load_app: App (widevine) does'nt exist, loading apps for first time
[75066.169144] QSEECOM: qseecom_load_app: App with id 187 (widevine) now loaded
[75066.273057] type=1400 audit(1499173224.876:2266): avc: denied { read } for pid=19764 comm="Binder:19752_2" name="address" dev="sysfs" ino=23761 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:sysfs_mac_address:s0 tclass=file permissive=0
[75066.277050] type=1400 audit(1499173224.879:2267): avc: denied { read } for pid=19764 comm="Binder:19752_2" name="/" dev="tmpfs" ino=5436 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:device:s0 tclass=dir permissive=0
[75066.298253] QSEECOM: qseecom_unload_app: App id 187 now unloaded
[75068.648773] QSEECOM: qseecom_load_app: App (widevine) does'nt exist, loading apps for first time
[75068.668092] QSEECOM: qseecom_load_app: App with id 188 (widevine) now loaded
[75068.799579] QSEECOM: qseecom_unload_app: App id 188 now unloaded
[75068.840965] type=1400 audit(1499173227.442:2268): avc: denied { read } for pid=19783 comm="Binder:19752_4" name="address" dev="sysfs" ino=23761 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:sysfs_mac_address:s0 tclass=file permissive=0
[75068.844863] type=1400 audit(1499173227.446:2269): avc: denied { read } for pid=19783 comm="Binder:19752_4" name="/" dev="tmpfs" ino=5436 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:device:s0 tclass=dir permissive=0
[75126.007364] healthd: battery l=57 v=3762 t=28.2 h=2 st=3 c=-788 chg=
[75186.069683] healthd: battery l=57 v=3823 t=29.0 h=2 st=3 c=-416 chg=
[75205.536484] SMBCHG: smbchg_external_power_changed: smbchg_external_power_changed: current_limit = 0
[75205.539776] healthd: battery l=56 v=3852 t=28.7 h=2 st=3 c=-192 chg=
[75205.540968] healthd: battery l=56 v=3852 t=28.7 h=2 st=3 c=-192 chg=
[75265.603220] healthd: battery l=56 v=3863 t=29.0 h=2 st=3 c=-134 chg=

Boot info:
Last boot reason: abnormal_reset

Could it be due to this?

[74660.445598] i2c-msm-v2 f9923000.i2c: NACK: slave not responding, ensure its powered: msgs(n:1 cur:0 tx) bc(rx:0 tx:10) mode:FIFO slv_addr:0x28 MSTR_STS:0x0d1300c8 OPER:0x00000090

I'm going to take more last_kmsg logs and see if the same error occurs before each freeze/reboot.