My computer Restarts, No Antivirus installed

[Nadeem]

As the title of my message, my computer restarts all alone! In fact, I have no anti virus so I wanted to download one but when I try to download, after 3% of my computer downloading stops. I went in 'system' and 'advanced' to disable the automatic restart but it does not change anything ...
Do you have any solutions?
Thank you in advance!

[Zachary]

when you start windows mode press "F8" -> start in Safe mode with network -> then download free avg antivirus as an example -> scan with the anti virus and restart your computer normally afterwards.

[Nadeem]

Here, I tried, but when I began downloading it restarted again. So same problem, even in Safe Mode with Networking! Another solution?

[.:MUNDITO:.]

Download any free antivirus from some other computer and then transfer it to your computer by any means and immediately scan for any viruses inside.