20.7 unstable for me, crash after crash, even a few reboots by itself

[twoblink]

I updated to 20.7; two days ago; and it's been crashing about every 12 hours or so; and I can't ssh to it or web to it; and so I can only hard reset (pull the plug; count to 10; plug it back) but right now; about half an hour ago; my firewall (sitting next to me) rebooted by itself; the box crashed that it actually rebooted.  And the reboot... didn't come back alive.  I had to unplug and replug.. and had to do that a few times.  It's back up now; but I don't know why.  there's no dump in /var/crash and dmesg didn't show anything specific.

I would like to be a useful soul; and so any help in pointing me where to look for the reason/ what logs to read; I'd be grateful.  Thanks!