There are traditionally two different types of speedometer drives. One is the mechanical drive which uses a cable from the transmission to turn a magnet inside a speedometer housing. The faster it turns, the more the speedometer head is displaced. If anything sticks due to dirt, a faulty speedometer cable, gears, etc, then you will observe the kind of behavior you have described. Fix...take it to a speedometer shop, if you can still find one. They can repair, calibrate, etc. OR take it to a dealership and they can replace it.
The other type of drive is digital, and an electrical signal is generated at the transmission sender. Eliminates the cable. The signal is converted at the speedometer to a display, whether it is an analog moving pointer type or LED display, or similar. The fix is the same.
It does not usually mean that there is anything wrong with your engine, or electrical system, or other.
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