2004 Chevy Impala transmission/speedometer

The speedometer will stick at various speeds(ex:60mph) and not return to zero. If not noticed right away, the sppedometer will continue to rise in mph every time you accelerate. To return back to zero, I can turn the car off/ then to on without starting and the speedometer will slowly (6mph each time) return to zero. It may work fine for several weeks, then do the same thing again. Is this a transmission, cable or electronic problem that I may fix myself?