For the past couple of weeks we notice the sewage pumb when it shuts down it shakes the pipes. You hear it start and than a second later you hear it finish but it rattles the pipes. Everything looks OK... Just doesn't sound OK

Sewage moving inside a pipe actually has enertia and momentum. The sewage passes through a backflow preventer and in your case that noise is the weight of the sewage slamming shut the valve. Valves are cheap and not hard to replace but I think I could live with this issue. If you secure the pipes they will not rattle as much but secure them with a vibration absorbing material like a foam wrap insulator