Folks, RV's are not Space Shuttles. The water system is a very simple system with a lot of plastic tubing and fittings. It is designed to be "water" tight, but it is certainly not "air" tight. RV water pumps work off demand. Open a faucet, pressure in the system goes down, pump turns on in an attempt to rebuild pressure. Close the faucet, pressure is allowed to rebuild and the pump turns off.
Occasionally, system pressure bleeds down, even with no demand on the system, and the pump will momentarily come on and bring pressure back up again. Your pump should not run frequently or for a lot of time with no demand on the system, but an occasional blip for a second or so every couple hours is not unreasonable or out of spec.
If you don't like the pump "burping" the system from time to time, turn the pump switch off when you are not actively using onboard water. This is a good practice to get into anyway. If a plumbing fitting were to fail or a run of pex developed a crack, you could fill your motorhome with the contents of your potable water tank in a matter of minutes.
