controller issue. please help.

i was playing halo 3, paused the game for about an hour, and came back. so the controller turns off for power saving, but i tried turning it back on and the guide button keeps flickering on and off but its not being recognized by my console. i don't have another controller and i don't want to turn my xbox off or i lose my checkpoint :(

please lemme know whats up.

try to resync it, or change the batteries.