Is it a laptop or a desktop?
Is it booting to the Windows logo and then restarting?
Turn off the system. Unplug the power cable and the battery(for laptops). Press and hold the power button for 10 seconds. Plugin the power cable and turn on the system.
Tap F2 or Delete to enter the BIOS menu. Let me know if the system restart from the BIOS menu.
Thanks & Regards