Error message that computer shut down with a problem

My Macbook Air (2020) has been giving me an error message that 'the computer shut down with a problem' even though I've closed all the applications and files and shut it down normally. I've been trying to find guidance about what may be causing this (files opening on startup, too much storage being used, clearing out diagnostic reports) and nothing has fixed it so far. This started fairly recently (last few weeks). I did the recent OS upgrade (to Sonoma) but still happening. There was an issue where my computer did loose battery overnight so did shut down by error, but that is no longer the case. Any ideas?