Speedo' Hangs sometimes

[1987stangman]

In the last week I have been having speedo issues. As an example, part of my DD is half hwy driving and during that trip the speedo would no go over 50Mph. The MPH would drop to zero when stopped but at normal hiway speeds it would never go over 50 and obviously I was going faster by 20. Turning the car off and back on would not help BUT the next day it works as it should.

Anyone else experiance this?