Random laptop shutdown, no BSOD, not overheating

[hellomyselftrick]

I'm having a very infrequent issue with my laptop (less than once every 2 months, possibly less) where it'll suddenly shut down with no warning or BSOD or restart. When this occurs, the screen will gently fade to black (not a sharp, sudden shutoff) and the computer will turn off roughly a few seconds after that. It's different than the kind of shutdown you get from holding down the power button. In all cases where this has happened, the system wasn't under load - no games were running, usually simple web browsing, word processing, or videos.

Things I've tried:
-Speccy is running and temperatures did not exceed 60C, so I doubt it's overheating.
-Windows Event Viewer is completely blank on the issue. There are events after the shutdown that note that the previous shutdown was unexpected.
-Under Advanced System Settings, I have the system set to write an event to the system log and perform a memory dump. However, there is no log or memory dump at %SystemRoot%\MEMORY.DMP.

What steps could I take to figure out what's causing these shutdowns if it's not overheating and there's no logs for me to look at?

 

[SugarPsycho]

Might be a battery issue? Try taking out the battery and running the laptop plugged in without the battery.

 

[hellomyselftrick]

It was plugged in the last time it happened, so I doubt it's a battery issue.