After installing macOS Big Sur beta my terminal behaves weirdly.
If I start terminal after PC restart I can start terminal just fine, however if I close it and try to start again I find myself at blank terminal saying "login".
I get the same problem with iTerm and native Terminal.
I'm having this issue as well.
This discussion from the Apple Developer Forums explains the issue and the solution.
Found the trigger, it's an iTerm2 thing.
Disable Enable session restoration under Preferences > Advanced > Session, after that you shouldn't have a problem.
Raised an issue with iTerm's developers. Not sure if there's something here on the OS side as well.