Every once in a while, always when my tank is full, or almost, when I start the car, the gauge reads empty. I sometime have to turn it off & back on a time or two before it shows a full tank. I have a 2002 Chevy Malibu.
Sounds like the fuel gauge sender, a cheesy little rheostat and float located inside your fuel tank makes a poor electrical connection…Or perhaps a weak ground to the dash circuit board that the gauge is mounted on…Both can be difficult to fix…