Other Fuel System Tank Assembly problems of the 2001 Chevrolet Silverado

Fuel gauge will drop to empty and fuel lights light comes on even though there is more than a half tank of gas I usually keep tank once it drops to below a half tank. Sometime I jingle my keys and it will go back up sometimes nothing.

I can fill my tank up of gas and it will say it is on empty. I have to use the trip all the time and this has even in happened on my 05 trailblazer too. And the seat belts on the 01 locks up while driving down the road and even on the passager side also please help.