Hello caeyal 
Turn off automatic rebooting
Right-click My Computer / Properties / Advanced / Startup and Recovery/Settings.
Under System Failure, uncheck the Automatically restart check box
You will then get a BSOD with error message which will help identify the problem.
Please post the whole error message.
Does this happen at any specific time?
Are you doing the same thing each time it reboots?

Turn off automatic rebooting
Right-click My Computer / Properties / Advanced / Startup and Recovery/Settings.
Under System Failure, uncheck the Automatically restart check box
You will then get a BSOD with error message which will help identify the problem.
Please post the whole error message.
Does this happen at any specific time?
Are you doing the same thing each time it reboots?