It's a common enough problem that it sounds like it's related to Windows Update. See this link for ideas. I don't know whether you can get to a screen where you can follow the steps or not.

http://answers.microsoft.com/en-us/windows/forum/windows8_1-windows_update/windows-8-restart-loop-after-installing-windows/44ea09cc-5e89-4581-85bc-aeee165b5bd4