My PC shuts down and about 2 seconds later starts again

[davidgpilot]

Hi, I have this weird problem for couple of months now.
When I press the start button to start my PC, it turns on, and immediately turns itself off, and after 2 seconds it's back again running and everything is normal.
It happens every time I start or restart my PC.
Any idea for a possible reason why it's happening?

 

[The Paladin]

When I press the start button to start my PC, it turns on, and immediately turns itself off

Are you saying that physically you are pressing the power switch on your case?
or
Are you saying when your telling windows (start/shutdown) to do it, it performs reboots instead?
I have seen windows 7 do this little act before, was never able to tell why.

 

[davidgpilot]

When I press the start button to start my PC, it turns on, and immediately turns itself off

Are you saying that physically you are pressing the power switch on your case?
or
Are you saying when your telling windows (start/shutdown) to do it, it performs reboots instead?
I have seen windows 7 do this little act before, was never able to tell why.

When I physically press my case's start button, it starts, shuts down and after 2 second it's back and running and everything is normal.