Car lurches when started, but still in "park"

[Marrs]

This has happened a couple of times from a cold start, but not always and rarely. When I start the car I can feel a distinctive surge forward, like it is in gear and wants to move froward but the transmission does still hold it still. Normally I have my foot on the brake when I start a car anyway, but I have tested this without my foot on the brake to see if it will still hold still and it does, but certainly wants to move.

My thought is it's something to do with the fluid coupling transmission, I know if you don't let off the accelerator pedal all the way when you come to a stop the car will want to pull forward because of the trans design, so if the transmission somehow coupled when I start it, maybe a throttle linkage is sticking, etc., making it surge? That's all just a guess.