Aporte original por: The Guy With the Hat ,
Have you attempted to reset the SMC? That would be the first step. Hold the left control, option, shift key and the power button for about 5 seconds and release. Then try to reboot. Might as well reset the PRAM as well. Hold command, option, P, R on start up until the machine restarts. If that doesnt' have any affect we'll have to dig deeper into a potential hardware failure.