I have this problem every once in a while. It seems to happen with a specific pump at the gas station we use, and doesn't matter how full/empty the tank is. I end up either turning the pump handle upside down to make it work, or just fill it really slowly. The slow method is probably safer than upside down handle.
As strange as this sounds and even though you probably already know this. Make sure the nozzle is all the way in to the tank. If it's half in it'll trigger the auto shutoff. Hope that didn't sound too strange.