Ok lets start with what toy hauler you have. Is this happening using the water pump or while connected with a hose?
The pumps that many RVs come with are cheap cheap cheap. Upgrading to a quality one will get you a better, smoother flow.
You may have stuff plugging up your line. Take the shower head off and see how the flow is, try banging the shower head (thread side down) on the counter to see what comes out. May need to clean the faucets too.
Again, the valve that controls the hot/cold water maybe cheap, broken or something else. If this is brand new I'd call the dealer and get it in and let them deal with it. It may need replacing.