A few days ago, my PC gave me a shutting down prompt and it turns itself off. Now, as long as the PC is plugged into the wall, my PC will boot up by itself, starts up for 3 seconds and then shuts itself off. I was unable to start the PC back up manually. Then after 15 seconds, and it starts booting up by itself for a few seconds and shuts off again. This keeps happening as long as it's plugged in. I unplugged it for a few hours, but as soon as I plugged it back in, it started booting up by itself again and shutting back down continuously. I replaced the power supply today, but nothing has changed. It is still giving me the same symptoms. Can anyone help me?