This type of rebooting behaviour is often caused by your computer overheating. You can check your system temperatures with SpeedFan
, which should give you an indication of whether your system is running too hot.
Also, I would recommend that you open your computer case and make sure all the fans are spinning okay and that there isn't an excessive amount of dust in there that would impede air flow. See the following Bleeping Computer
tutorial for guidance on cleaning inside your computer.Cleaning the Interior of your PC