Problems filling fuel tank

I have a 2002 Hyundai Sonota LX, 98,000 miles, 6 cyl, 3.0 liter engine. For the past 2 weeks I have not been able to add fuel to the tank without the pump shutting of every 20 or 30 seconds. I know the tank is not full because if I perservere and stand there for 15 minutes or so, I can finally get 13 -15 gallons to fill the tank. This happens at any service station I have tried. The pump keeps shutting off every 20-30 seconds while pumping fuel as if the fuel is backing up to the filler tube.