Why shutting down?

I have a Yamaha A/V HTR-5890, runs from a few seconds to 2-3 minutes, then clicks off. I have had it for a couple of years, no changes. I run a 10" Klipsch sub, Chorus Klipsch speakers, along with some older duel 12" MTX's, and a older smaller Advent's for surround speakers. It has never run hot, this is my shop system, so it's colder out there then inside.