Computer resting every 3 seconds

[mattberge]

I have done the flowing to try and fix the problem

Taken out every component except the cpu and psu, the problem consists

Put each ram stick in every slot

Started the computer without the case power button

Reset the cmos

I was looking at what parts to replace and I don't know what to go with the cpu and MB or a new PSU?

I work on the computer for my school and work pretty frequently so I would appreciate any help.

 

[schooltime7634]

Is it literally 3 seconds, or is it just frequent, like 5 minutes? It sounds like a system setting.

 

[Greeko85]

If its a continuous on off sequence it could mean that something is shorting. Was this a working pc that suddenly developed the issue?