Could be a power supply problem, maybe dry soldered joint or component breaking down. So best get it checked out. If it only goes off at higher volume settings, could be fan is faulty (if one is fitted in amplifier).
Also, with erratic operation it 'may' just require a reset with a Panasonic firmware recovery disc. Your Panasonic dealer should be able to try this for you. (Just like flashing a bios).
Cobweb
January 2005