Shuttle boot problem

[SilentVixen]

Before I go buying things to fix my computer, I want to be sure what's wrong with it. Here's the deal:

Once it's been turned off, you push the button to turn it on, but nothing. Unplug it for a few minutes and it will boot just fine. What would cause this?

Thanks
~SV~

 

[SilentVixen]

any ideas?