Hi - last nite was testing my rear speakers as I was sure that the rear right was clicking on and off intermittently

found that it the rear (both sides) and the sub that clicks in and out
currnetly have just the HU set to rear fade so I can see how long they are out for and if it comes on over bumps etc. but seems to be off for long periods at a time and come on of their own accord

what could poss be wrong ??
Dodgy connection or knackered Amp. ????

Really really [censored] annoying - whats the best fix ?
(without tearing the car apart and replacing/upgrading stuff at mucho expense ?)