I had this problem, intermittent is the worst; whenever I sent it for repair, it behaved 'normally' until it came home again! Try talking to it, (nicely) And don't call me 'nutty', else why does everyone talk to their car?, Machines have 'spiwit' ['Fwee Bwian], When I got my first PC, my video packed up just out of jealousy. same day. (same time.)
"Sounds" like a loose speaker wire, or a speaker wire with a break somewhere. Replace speaker wires. If problem persists, then at least you'll know it's not the speaker wires. Actually, it's highly unlikely that there would be a disconnect in left AND right speaker wires, so you already know it's probably not the speaker wires. So, something after the VU meters and before the Output; When the sound cuts out, can you still hear it on headphones? Could it be a break or dry joint at the amplifier. Got a circuit tester? You possibly need better help than this...