I have this problem also since upgrading to from Bridge 2018 to Bridge 2019 (18.104.22.168). Sometimes when I start Bridge I have to re-enter my Adobe password. It doesn't happen every time, but I have not yet figured out the pattern of behaviour.
Starting Bridge CC 2019, it is required for a user to be signed in Adobe Creative Cloud in order to launch Bridge.
So if you log out on your machine and launch Bridge, it is expected to sign in again before using Adobe Bridge.
Thank you for this information - this explains the behavior I am seeing in Bridge.
However, I shutdown my PC every day and it is not in a public location. Therefore I do not benefit much from this increased security. I use random passwords so I cannot simply remember my password - I have to log in to a password vault to get it. I would like a checkbox added so that Bridge can optionally remember the CC login credentials.
Furthermore, if security is so important, why does Bridge quit without an option to sign out of CC? The new policy seems to have been implemented inconsistently in my opinion.