Computer restarts randomly?

The most likely problem is the power supply. They do start to fail commonly. When it comes to the a/c power from your outlet, you can notice it by the surrounding appliances and lights dimming or turning off. If they aren't doing that when your computer is rebooting, it's most likely the power supply.

One of the most common power issues is that the fan inside your power supply is not spinning that's the first thing to look at look and see if the vents on your power supply or plug with dirt and if the fan is spinning get yourself and air compressor and blow the dirt out of the fins of your CPU and of your fan random shutdown will also happen if the heat sink between your CPU has need of regressing with heat sink compound the sign of this is the CPU fan constantly running check those things first and get back to me if it doesn't help you

Read how to troubleshoot Windows computer restarts without warning

Does the computer turn it self off? or it just restarts?

if the computer just restarts it's likely a software issue, not a hardware issue.

You may need to take the computer to a local computer store for repair if you don't know how to fix these computer issues.

It's alive!