My NUC8i3BEH has gone AWOL a couple of times in the past week. Upon checking, it had powered down on its own, most recently while I was listening to an album.
Since I’m using ROCK, there’s no log file I can check, so I’m open to suggestions regarding possible cause.
Overheat? is there a dust bunny or kangaroo in the fan?
Any power flickering lately?
There are logs but going to power off is very odd indeed. Normally it’d just lock itself up if it was a software crash. You doing anything fancy with power supply? Overclocking? Etc.?
Thanks, @bearFNF. Would the NUC initiate a shutdown under these circumstances? Anyway, I’ll check and report back.
I just confirmed, via an old post from Danny, that ROCK doesn’t do anything with thermals.
So, check your BIOS settings to identify what thermal limits are set and what the system shall do when those thresholds are crossed. Some systems will certainly hard power down to protect themselves so this certainly could be the issue.
I feel silly asking you this, since you are the moderator par excellence, but… do you want this to be in the support section?
Okay, all sorted now. Thanks everyone for your input.
First, there doesn’t appear to be any obvious settings in the BIOS to initiate a shutdown if temperarure reaches a threshold. However, it was clear that the NUC was running hot since the fan was on a boot and stayed on. After a couple of minutes (in BIOS settings) temperature was at 55 °C.
So, I stripped down the NUC, cleaned the fan and heat shield.
It’s running now with no fan noise. 
I’ll check temperature tomorrow when SO isn’t watching TV.
Since I suspected hardware, I thought this the best category.