What Does 3 Red Flashing lights mean for xbox 360?

360 is working very fine.. Used it before and then i turn it on now. I see 3 red lights flashing and the upper right corner there was no light.. i tried again same thing.. Then i waited 10 mintues and it worked. Turned it off and back on and it doest work now.. Ive look online but i cant tell if its hardware failure of overheating.. does anyone know.. thanks