Automatic reboots can be caused by several different things and are hard to diagnose. One thing you can try is turn off the automatic reboot option under the recovery options for your computer. This will make it so your computer won’t reboot on errors so you can see any problems. Following are the steps to stop the computer from restarting again and again just right click on the My computer and select the properties from the menu and click on the Advanced Tab and below that you will see the startup recovery and click on it and select the setting to open the dialogue box and remove the tick mark from the box which says automatically restart the computer and after that click on ok and restart your windows.
And check whether you have installed faulty drivers or application through which the error reboot the system or else check your RAM or upgrade your motherboard BIOS setting very carefully.