Ascetic minimalistic retreat near a main road with all kinds but also two organic food supermarkets (open till 9 p.m.)
The advantages (quietness, even on weekends, a lot of space, quick hot water in shower, tidyness, good hard matress (1,40m width I guess) all devices worked fine, good and reliable WiFi, very nice communication with Susanne) compensate the disadvantages (no sink aside cooking/preparation place, but 5 metres across the room with only cold water, very tiny not practical bath, no microwave, no TV, no way to darken the room because of the window in the roof, no carpet, only wooden floor, bath door not closable).
I wouldn’t call it central, but public transport in Berlin is great. 100m walk > bus station > 20 minutes to Main Station (Berlin Hauptbahnhof).
45 minutes energetic walk to Potsdamer Platz. 30 minutes engaged bicycle ride to Grunewald/Wannsee, 20 minutes to Friedrichstrasse (at least on a quiet Sunday morning :-).
I enjoyed the place very much, I stayed on my own in Hauptstr. 140 in Sep 2018 for 8 days. And certainly would consider staying there again when coming to Berlin.
(I did not have any problems with neighbours, (as some here mentioned), I didn’t even saw them)