Computer turns on, turns off then turns back on but has no video output

After getting a couple blue screens I am having the following issue:

When I turn my computer on, the fans and drives all start up. After approx. 2 seconds the computer shuts itself off. After another 2 seconds the computer turns itself back on again. This time it stays on but i have no monitor output. I don't hear a beep which tells me it is probably not posting.

I have read a few other threads that have a similar issue but not the same. I am thinking it is either the mobo, GPU, or PSU.

I would like any guidance and assistance that you guys can give me on this specifically what i should look at first and how to diagnose. Thanks. system specs below:

ASUS P5Q Pro ATX Intel Motherboard
Intel Core 2 Duo E8500 3.16GHz LGA 775 65W Dual-Core Processor
EVGA GeForce GTX 260 Core 216 896-P3-1265-AR Video Card
Antec EA650 650W Power Supply
OCZ 2GB (2 x 1GB) 240-Pin DDR2 1066 (PC2 8500) Dual Channel Kit Memory

Motherboard Short

I have helped somebody who had a similar issue and it was the motherboard being shorted out by the case. We took the motherboard out of the case and it booted up just fine. Something you might want to try before purchasing new components.

if this is the issue, how do I get it so it doesn't short in the case?

To make sure that is the problem you will need to pull the board out first then try it on a non-metal surface. If it works then you will need to address the case issue by putting the board in with out the screws to hold it down and try to turn it on. If that doesn't work you will have to examine which part of the mobo is touching the case from underneath

i had to take the graphics card out in order to take the mobo out. just out of curiosity i turned on the comp without the graphics card and it started up. still didn't hear a beep for post but at least i don't have it turning off on me. will let you know when i have the mobo out and tested.

alright...

I took the mobo out and started everything up. everything spins up fine (still no post beep though) then after about 15sec it automatically turns off and doesn't come back on.

Are we looking at an overheating issue?

What is the next step?