Omega B Caravan 2.5 DTI automatic jerks/wummers when taking gas at 50-70 km/h

Hello your loved ones, after 2 FOH didn’t know any advice, I ask here if someone knows the problem and maybe also the solution. My Omega (Bj 02) jerks when taking the gas. Most clearly with a cold engine / gearbox and between 50-70km/h when I take the gas away and the car goes into the thrust mode. The jerking feels as if some mechanical part is running unround. At the same time you hear a slight whimper. Sorry, is not easy to describe that well. I could not even say whether it comes from the gearbox or from the chassis or the engine. Anyway, it has become significantly stronger during the last 5,000km and I wanted to know before I eventually left the car at least what it is. Maybe someone has already been able to solve a similar problem before. Alas, I forgot to mention one thing, although I did not know if it had to do with it again: I had left the car in the ski holidays a week ago. On the day of departure I drove the car and had already given the feeling that it was unbelievably good for the valley.