Question Computer reboots after mains power turned OFF

[BBGM]

Hi, my first post here and possibly something of a strange one.

A couple of days ago for no apparent reason my computer began rebooting after shutdown. I've scoured the internet for fixes and tried every solution I've found, with no luck whatsoever. The computer continues to restart after shutdown.

But tonight something happened which I'm fairly certain is completely impossible. I shut the computer down and as expected it began to reboot. Out of frustration I hit the computer's power button to kill it. Then I cut the mains power, flicking the switch off at the wall.

And the computer continued to reboot until I physically pulled the plug out of the wall about 5 seconds later.

I'm curious if anyone else has ever experienced this, and if so, what caused it. Because if the mains power is cut at the wall there should be NO way a PC can continue to boot, right? Not even for a few seconds.

PS: We're not talking about a laptop with a battery, this is an old desktop PC.

Thanks in advance for anyone who may be able to explain this weirdness!

 

[lvt]

What desktop PC do you have?

Are you sure that the PC isn't connected to some sort of UPS?

 

[lvt]

UPS = "uninterruptible power supply", a small battery pack sitting somewhere near the computer that is capable of providing the electricity for a couple of minutes after you remove the wall plug.