fuel gauge problem

GA_googleFillSlot("Forums_ROS_300x250_noad"); Today I started my 2000 Dakota and the low fuel alarm sounded and the fuel gauge showed empty. I knew there was a full tank. So I shut the engine off and restarted it and the gauge showed full again, what I expected. I had to make several stops - bank, super market, ect. After starting up after each stop sometimes the alarm would sound and the gauge would show empty and sometimes it would show full. Any ideas as to what I should check?

Thanks
beach