1995 E 320, automatic,SW, Cruise control?

[Qamar]

While driving on slightly less then 80 Km whenever i apply the cruise control option the car takes slight jurks as if someone is puching the acclerator pedal and then relizing it. Surprising when i apply the cruise control on exactly 80 km speed, the car is ok, and there are no jurks.

The same position happen if i apply the cruise control slightly below 100 KM speed, whereas the moment i fix the cruise control above 100 the car moves like a silk. (No jurks)

What could be the problem. Any feedback will be highly appreciated

Regards