Amplyfier Going in Protection

I have a Cadence FX500 Connected too an Alpine player by 3 RCA cables, and " front speakers 2 back and 1 Sub. it's a 5 channel amplyfier. When I play music it works just fine then it suddenly goes in protection mode afther a random amount of time varrying from 2 secounds too 5 hours with adjusting on all the crap but it still goes in protection and when it does it wont work at all for a while. it's not hot at all, and the Player keeps going, checked for short circuted wires. have no idea what too do. Can this be anything with incorrect Input Gain levels and/or Hz setting on the Amp? or mabe bad grounding.? apriciate any help.