kernel panics on sleep, M1 Macbook Air Big Sur
I believe I'm getting the same problem/fault.
New iMac Pro with clean install (obviously) of macOS 11 (from today 11.2.1) three times in 60 days I have come back to an unattended (and so, presumably sleep-induced) ungraceful restart with the login (not wake) screen. But - in my view, significantly - 57 times I have left the machine on and come back to everything normal.
Twice I have had a k/p on shutdown - also (I believe) related to some sort of timeout… external device(s)? Not iPhone.
Happy to share logs. But don't know my way around (system?) logs well enough to know which, where and what to look for.
kextstat reveals only Apple kexts installed.
The only other thing I do think might be relevant is the fact that my Time Machine icon in the Finder sidebar often spins for several hours (!) after a TM backup - and the logs show multiple lines like these:
Feb  8 16:51:44 iMac-Pro com.apple.xpc.launchd[1] (com.apple.mdworker.shared.05000000-0500-0000-0000-000000000000[20917]): Service exited due to SIGKILL | sent by mds[115]
Feb  8 16:51:59 iMac-Pro com.apple.xpc.launchd[1] (com.apple.mdworker.shared.02000000-0400-0000-0000-000000000000[20924]): Service exited due to SIGKILL | sent by mds[115]
Feb  8 16:52:56 iMac-Pro com.apple.xpc.launchd[1] (com.apple.mdworker.shared.02000000-0500-0000-0000-000000000000[20941]): Service exited due to SIGKILL | sent by mds[115]
Feb  8 16:53:32 iMac-Pro com.apple.xpc.launchd[1] (com.apple.mdworker.shared.0A000000-0300-0000-0000-000000000000[20902]): Service exited due to SIGKILL | sent by mds[115]

often by the hundred; which make me think more than ever of failed time outs.
TIA for any guidance :-)