wec3

I have a 2001 S4. I'm wondering what might be the cause of the following ....

After starting the car and moving forward (whether in gear or neutral), the car will roll smoothly for 5-10 feet and then there is a feeling of rolling-resistance (for lack of better word). It's like going over a small speed bump (not the bounce but the resistance). It's just for a second or two and then back to smooth rolling. It doesn't happen again for as long as the engine is on. If I turn off the engine, start the car again, it will happen exactly the same every time. Perfectly reproduceable. (By the way, it doesn't happen when rolling in reverse. It only happens the first time rolling forward after starting the engine).

My mechanic is a bit stumped. He says it is like some pump is being triggered and once it's triggered, every thing operates as it should. He's just not sure what pump it might be.

Any experience with this or thoughts about it?

Thanks

Bill