After the computer restarted Bitlocker requested me to enter a recovery key out of the blue:
Bitlocker needs your recovery key to unlock your drive because the Boot Configuration Data setting 0x25000020 has changed for the following boot application: \Windows\system32\winload.efi
The only thing I did before this was Comodo Firewall installation. While I can’t link these events with certainty, I have no other ideas so far. So, I wonder if anybody else ever faced the same problem?