Complete shutdowns are usually caused by hardware problems and there’s a lot to choose from but occasionally spike protection in bios is just too sensitive especially with todays high powered gpu’s that probably weren’t even tested on some of the first revision mainboards around. Usually a bios update would address this so check that you aren’t still on the same ones that came originally installed. MAKE SURE YOU KNOW WHAT YOU ARE DOING BEFORE FLASHING NEW BIOS, if you are not too sure then get help from a techie.
In a way I am afflicted but in my case it’s the rcd on my house wiring that trips when I switch on my PC’s rear switch. To make things even more baffling this only happens if my monitor is plugged into the gpu and remember this is before the PC is even switched on at the front. It’s a 16 amp rcd and apart from my PC there’s hardly any load on it so zero chance of overload.