Unusual Vibration - 986 w/ TIP

[Seadweller]

What would cause a "rolling" vibration in a 986 with Tiptronic? The engine is running like a sewing machine, but every once in a while I get an off and on, rolling, heavy vibration that shakes the wheel and seats quite noticeably. Only happens in gear while stopped. I should add that the idle speed is rock solid.

I wonder if it could be related to another symptom. In manual mode, the car makes a solid shift into all gears but 2nd. Coming out of 1st into second, it shifts softly, and feels like it glides into second, rather than a crisp bump into gear. I thought perhaps this might be part of the TIP learning algorithm.

Thanks!