Computer problem
2003 Ford Taurus 6 cyl Two Wheel Drive Automatic 55,000 miles

I have a recently purchased 2003 Taurus. When stopped the non digital spedometer will go from 0 to 40 MPH and back again. It has done this three or four times in a month. Yesterday the car stalled twice and the spedometer performed its up and down technique after both stalls. The dealer can find no problem,

SUggeest action? Are the two problems possibly related? Should I increase the idel speed ?

Thanks