1999 Mercedes C230 - Lurches after starting

For several months, after my car sits for six hours or more, it lurches/halts as I give it gas and start driving. This last for about 1/4 to 1/2 mile and then the car smooths out. The problem will not reoccur unit the car sits again. The vehicle has 73,000 miles. There is no check engine light on. Back in the summer, the light came on and I had the air mass sensor replaced. I recently had the gas actuator replaced, and the vehicle is not really any better. The car is currently in the shop and though the mechanic can duplicate the actions of the car when driving it, there is no code on the computer confirming what the problem is. Can you please help me? I would like to get the car fixed in order to sell it, but right now I am in limbo. Thanks.