Sorry,should have been more specific.I meant the fuse running off the positive side of the battery,on the power cable.
If the fuse isn't making a good connection or the wires at the fuse.But an exposed wire touching the chassis can make it cut out.Just check all connections and wires.

It can only be the amp or the wiring.

The wires should run down the side of the car under the trimming.That just pops in and out.It's not hard,just follow the wiring.

There's a grounding strap off the amp,if it's too short that can cause it to cut out.

Is the amp old,it happens over bumps,could be old sensitive.But probably the wiring.