[shawley]

Do you have full 12-14 volts with a multimeter at the amps?

Protection is normally bad ground, bad amp, bad speaker, bad fuse, etc.

If both amps are doing it, check with a meter, make sure you have full 12 volts,

If you do not, you could have a bad fuse that is partially blown.

Could easily also be a bag ground for the amp, loose ground, bad ground from battery to chassis, or a corroded ground.