My Dell Precision T5600 not turning on

Hey PPL,

I was trying to switch on my T5600 today, it kept restarting for few times by itself and later it just started and nothing showed up on the monitor.

I've tried:

1. Unplugged all cables and pressed Power Button for 30 seconds
   
2. Switching the cables for the monitor.
   
3. Switching from Display to DVI
4. Switching to another monitor

If nothing works out, I've to call DELL Service Centre. Is there anything I should look out for before calling DELL?