That used to happen to me A LOT. Right now it only happens because I have a faulty RAM that I’m planning to replace very soon, but before that, I think the CPU was overheated and it forcefully rebooted my laptop, at least that was my impression by the logs at boot.
After a long time of debugging, I decided to, first, disable hibernation to see if that was a problem, then I disabled CPU boost and I think that was the cause of overheating, since, for some reason, my distro decided that it was a good idea to use CPU boost for any common task and it caused overheating.
I haven’t had any problems not related to faulty RAM since then lol
I’m self-hosting in a 500GB HDD, 2 cores AMD A6, 8GB RAM thinkcentre (access for LAN only) that I got very cheap.
It could be better, I’m going to buy a new computer for personal use and I’m the only one in my family who uses the hosted services, so upgrades will come later 😴