Search for Windows Event viewer online and you'll find plenty of hints, videos etc.
Or check the windows implemented search, WIN key + type "event viewer".
-> Check online how to handle and search in it properly.
Ok if the power supply is good enough it could also be a broken USB port where the inner parts are "connecting to each other".
Or if you sometimes get "neon green/purple" sprinkles on your screen the GPU is maybe overheating.
So you need to clean it from dust, but be sure to be gently and check online how to do this without damaging it (without power connected at all!!!), especially the fan needs attention. You should block it so it does not runs too fast by the air stream of a vacuum cleaner).
Or if it just turns off without any error message the RAM could be a problem as well. You could get a RAM check tool online, like: "MemTest" (or others).
Or (but I do not think this would crash the pc totally. It could freeze but shouödn't turn off immediately) the harddrive is damaged. Check the hdd's SMART state in the bios + let windows do a harddrive check for bad sectors.
If the PC really just switches itsself off it got to do with too much energy consumption at a time, or maybe a broken motherboard, or a internal short circuit like with a USB connection etc.
Last idea:
Check online with your motherboard name and model number + gpu name and model number if there are similar issues reported by other users.
Maybe ask at
www.tomshardware.com or others
But be sure to provide all information like windows version, patch level, motherboard, gpu, cpu, cpu cooler, temperatures, etc.
Everything you get from your bios or windows hardware manager, so they can help you.
Btw: Do you play any other games with a good CPU and GPU usage, like newer online shooters?
Are they suffering from the same problem?
If not it could be some ESO issue, like the engine used for ESO, or a driver issue for you as well.
Maybe install earlier/older GPU drivers again?