1995 E 320, automatic, SW,Cruise control?

[Qamar]

Whenever i apply cruise control on 118 Km, 138 Km the car keeps on herking wheras when the figures are rounded up like 120Km, 140 Km there are no jerks during the cruise control operation.

I have checked the tire pressure. All the four tires have the same 35 PSI in them. All the four tires are also of the same number & size.

Anyone who could tell what could be the problem. Any connection is loose or what could be the reason for these jerks. They are like giving accelator and leving it, then giving it and then leaving it...