Please help my w124

[300 CE ray]

My 92 mod 300 ce w 124 started to give me trouble today.
It have 143 000 miles total.

At any speed when pedal is depressed and hold steady,everything is normalt, or even when I let go the pedal totaly and the car start to deacclerate.
My problem starts when I let the pedal out just a little bit, etc I overtake a car from behind and just ease out on the pedal and the car start to run rough and hesitate/sputter.When pedal is depressed again it accelerate just fine.
Also on hard take off everything is normal.
Any one out there that know what this could be??
Any reply is highly apprechiated.
Ray