Well, I would certainly hope the transmission should "ease into" gear when you move the stick.
You do understand that the movement of the stick is actually only operating a hydraulic valve in the transmission and any movement of the stick at all will produce some motion on the ground?
I hope you are not simply yanking the stick as though you were trying to select a gear on a manual transmission. ???

Yes, the tractor rockets forward and backward even by slowly inching the stick in either direction.

Does there seem to be a lot of free play or "sloppy looseness" anywhere in the linkage that connects the F-R control lever to the transmission control bellcrank?