Weird problem

Hi everybody!

I didn't quite know where to put this, so I hope this is correct.

Recently my computer has started acting very strange. When I press the power button, the fans begin to hum, however the pc doesn't appear to boot. The screen remains off and the standard 'beep' isn't played. If I wait five minutes and reset it, it normally starts up at normal.

Does anyone know what is causing this and/or how to fix it?

Thanks for the help