Strange issue - PC turning itself on

[V4NT0M]

This started happening a few weeks ago, it only happens sometimes but I'm a bit baffled...

1. Shut down PC with power button.
2. 5 minutes later the PC switches itself back on.
3. Shut down PC with power button.
4. Immediately PC switches itself back on.
5. Shut down PC with power button.
6. PC Stays off.

As I said it doesn't happen all the time but when it does happen it's the exact same scenario. It doesn't switch itself on at any other time.

 

[V4NT0M]

It's a newish build place so I can't imagine there would be any ghosts about and I can't think of anyone that could be haunting me.

I haven't checked any bios settings but not sure what setting it could be as it doesn't happen all the time.

I'll check my cables tonight. My first thought and still my leading theory is that it is the "switch on after power failure" option. So probably something to do with wiring I guess.