It is a glitch in the redundancy safety feature where the console overheats and needs to cool down. Generally this will occur after the console has been on for prolonged periods of time and has been put into sleep mode (normal off mode).
What you need to do is press and hold the power touchplate/button to turn it on for at least 5 seconds. This will not actually turn it on, as it already is on and completely unresponsive (in a coma). What this will do is do a hard power down instead.
Give it about 30 seconds, and press to turn back on. It should start up again with zero problems.