A few days ago we named our M1 Air "Crashy". As noted above after reinstalling Big Sur Crashy went from restarting every 3-4 hours to restarting every 2-3 days. Since we were nearing the end of our two week return window we installed Big Sur 11.2 the moment it showed on 2/2 AM. We told Crashy that if he did one more restart prior the end of our two week return window he was out the door (we confirmed deadline was midnight PT 2/5)
Crashy has not restarted since. So, for better or worse, he's ours now. We are going to keep the name Crashy however.
I got a hint from Apple tech support that there were firmware/macOS version problems from some of the factory installs. I've seen these kinds of crashes on my Intel Air when I downgraded Mojave to get around a screensaver bug (that was fixed the day after I downgraded) -- they resolved on the Intel machine when I went back the latest Mojave release. I think Crashy had the wrong firmware for the factory shipped macOS Big Sur version.