Unround motor run (after cold start)

Hello, our Fox has (again) a fault… When the Fox is started it runs quite normal, then I give a bit of gas, it starts to jerk completely. If I keep the accelerator constant at approx. 2000 revolutions for a few seconds, then the engine is running quite normal. The problem also strangely only occurs at the cold start or if the car stood up for a few hours. Maybe someone had similar problems and possibly a solution? Before I invest money at the VW dealership un d possibly parts are exchanged which are not then after all, I prefer to ask here for 🙂 Blessings mdcc PS: of this problem and the problem with the cracking clutch, I am actually quite satisfied with Fox, that only once as a note.