My PC Self-reboots 1: Electrical input problem
I’ve experienced this problem a few times myself and it only took a couple of self-rebooting for me to get annoyed at my PC. There are five reasons why a PC starts to self-rebooting, I’ll have to break this post into five different parts.
It’s possible that there is a problem in the connection of your PC to the electricity supply.
Plug the PC properly into the wall socket.
Plug the main leads properly into the back of the PC.
If your PC is using a multiple adapter, plug the adapter properly into the mains. If that does not work, buy a new adapter.
If the main plugs include a fuse, replace it.
Source: Answers that Work