93 Altima Speedometer / Transmission

I just found this forum and need some help. Have a 93 Altima w/automatic trans. Intermitantly when starting cold the speedometer will register 30-40 mph while sitting still. If you start moving it seems to settle down and work fine. But also when it does this the transmission will stay in 2nd and not shift untill you shut the car off then restart then everything is fine. Any help would be greatly appreciated.
Thanks,
David Bauers