2002 Ford E-250 gauges problem. Need help!

I have a 2002 Ford E-250 with weird gauge problems, while I'm driving all the gauges (battery, speedometer, oil pressure, etc) suddenly fall flat and don't even move for about a minute. Then they will jump high and go back to normal. Other times they just bounce back and fort. Any idea on what could be wrong? Battery is new, just in case that really matters.

Thank you.