2005 Ranger filling problems

When I'm filling up at the pump, it shuts off within a couple seconds like it's full but it's not. I have to stand there for 20-30 min feathering in gas every few seconds. I want to try and fix this myself but don't know where to start. What can be causing this "pinch off" or "back up"? Can I fix it myself? what part/parts do I need or should I look at? Is there another thread that I missed already talking about this?

Thanks!