You'll have to ask Sony. Game consoles are black box systems, and only the manufacturer's really know what's going on inside. The system could have been damaged during your last gaming session, and you just didn't notice the effects until now. Either way, you have to call Sony about possible warranty repair work.
I usually leave the rear power switch on (red light).
Today I did not have a light.
I turned the power switch off then on - nothing
I unplugged the power cord and plugged it back in and I got the red light back.
When I press the power button it turns green, then quickly yellow and beeps 3 times and then flashes red.
The sony site says something about overheating but the system was off all night.
Any help would be greatly appreciated.