LoL causing PC to shut off?

So about a week ago or so, my computer has been shutting off randomly while playing LoL. But I've noticed that it only shuts off when I plug in my charger and I play LoL with the charger connected. My PC doesn't shut off when not plugged in though. Plus it hasn't been shutting off when I use it on any other thing but LoL. Like if I surf the web while charging, nothing happens. Someone please help. Thanks.