Interestingly enough, the issue seems to have finally resolved itself on my Mac Mini (M1). After seeing this message every day since updating to 12.2.1, I decided to login using my Administrator account to have a look at the security logs (for security purposes, my normal login is a Standard User account). On login, I received the "your machine shutdown unexpectedly, do you wish to send logs to Apple" (or something similar). I selected OK and submitted the logs. I did some digging in the "shutdown_stall" logs but not finding anything useful, I rebooted and logged in as usual, but noticed that I did not receive the "shutdown" warning message on login. It's now been gone for two straight days! Perhaps logging in that once using my Administrator account cleared a flag of some kind that my regular account did not have permissions to correct?
It could be a fluke, but figured I would report back to let other people know about this...