What would make it do this

Hopefully it's an easy fix at a good tranny shop , I guess that's where I would go

Go to a good transmission shop and have them check it out. A lot of transmission problems can be cured with shift solenoid replacement, so here’s hoping yours is just that.

Site error

If the car will move in reverse but won’t go forward, the likely cause is worn out solenoids, clutches, and/or gears. Check the transmission fluid, as a low level is a potential reason for making the car move in reverse only, especially if it jerks like yours. But more likely, a repair or rebuild is in your future, and a religious maintenance schedule will make a trans last a lot longer.