My PC always turn off after start sometimes display press F1 to reeboot I press but nothing happen and its still continue display same things press F1 to reboot

Do you see any type of screen before it shuts off? Can you enter BIOS or selctive startup before you receive this message?

If you see a quick blue screen before it shuts down or restarts then it's very often a corrupted Registry and there are tough to fix, certainly not by directions in a forum. Your best hope is the repair function of your OS CD.