I had my sender replaced under recall. The gauge appeared to work normally but would still indicate a round a 1/4 tank when it was actually empty.
It might be that it's a problem with the connectors at the back of the cluster. Next time it does it try giving the top of the cluster a whack and see if it moves. There are a few threads about cleaning the cluster connectors if you search.
Also try pressing the odometer reset button, turning on the ignition then releasing the button. That will put the cluster into a test mode and all of the gauges will swing back and forth. The small gauges should run in sync. If the fuel gauge doesn't move like the others you might have a screw loose on the back of the cluster.