You should configure the startup options of your computer to have the hard disk drive first in the boot order, before any other drives such as CD/DVD drives or USB drives. If the hard disk is not first and you typically boot from hard disk, then a boot order change may be detected or assumed when removable media is found during boot. The boot order typically affects the system measurement that is verified by BitLocker and a change in boot order will cause you to be prompted for your BitLocker recovery key. For the same reason, if you have a laptop with a docking station, ensure that the hard disk drive is first in the boot order both when docked and undocked.