i know this is a very old post but im hoping you got to the bottom of this? i bought a new mk4 2.0 gti last week and it has this exact same issue i've cleaned the throttle body and the issue is completely random, sometimes it does it sometimes it doesn't...
i'm hoping you can tell me what you did to fix it so that i can fix mine without spending a lot of money especially as i cant afford to spend loads.
please email me