I am going to say welcome to the forum
@Tatla.
Most of the posts in the subwoofer area are for subs installed at home (not in the car).
There is probably a place on the forum for car audio, just look through the threads.
To me, the most obvious causes would be loose connections.
If your vehicle is moving and the problem occurs, but it does not occur when your vehicle is not moving, then that eliminates clipping and other overdrive conditions.
The most obvious problem for cutouts when you move that dont occur standing still is loose connections.