Win 7 Restarting itself

My computer has recently started to restart its self intermittently without any warning or blue screen.

I have updated my nividia driver and now it happens less(every half hour instead of every 5 minutes.

Please help and thank you in advance :)

How old is your system? When was the last time you blew the dust out?

   Warning

Before you proceed with the following, answer these two questions: Are you still under warranty? Does your warranty allow you to open up the machine to check hardware? If you are unsure of the answers to these questions, contact your system manufacturer. WARNING: The steps that follow can void your warranty!!!

To remove dust, follow the subsequent general procedure. If you have a desktop bought from Dell, HP, Sony, Lenovo, etc. make sure removing the desktop casing will not void your warranty first. Call the company if you are still under warranty and ask if it is okay to remove the casing and blow dust out. The procedure described is fine for laptops; just make sure no stickers are on panels saying if you remove the panel it will void the warranty.

1. Shut down and turn off your computer.
2. Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
3. Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
4. Remove the casing for a desktop, or remove any screwed on panels and disc drives for laptops.
5. Blow out the dust inside by using a can of compressed air or a low pressure compressor. You will want to put the computer on a desk or table so you can maintain the can in an upright position if using a can of air. Blow into all crevices on the motherboard, heat sinks, cards, modules, etc. for a desktop. Blow into vents, opened panels, disc drive areas, USB ports, and the keyboard if it is a laptop. You may also want to blow inside the disc drive by replacing the drive to the laptop, starting the computer, opening the drive, and then turning off the computer and removing all power as described above including the 30 second power button step. For a desktop, you may also want to blow inside the disc drive by starting the computer, opening the drive, and then turning off the computer and removing all power as described above including the 30 second power button step.
6. Replace casing for the desktop. Replace panels and disc drive (if you have not already done so) for the laptop.
7. Plug power supplies in. AC adapter for the desktop. Battery and then AC Adapter for the laptop.
8. Start the computer and see if performance is better.