Omega B automatic jerks when starting

Evening guys Have there a little problem my omega b 2,0 16V Bj 94 automatic takes the first few sec. not really gas on when driving fast (e.g. from the traffic lights) or rather he jerks. That’s also me at about 100 when I give gas and he turns off `n 3 in 4 noticed And what worries me even more is that he was sitting a few days ago (if I drive quietly he somehow has no breakout) he at about 80 no gas anymore I thought it was just a louder and louder knocking (give it to the gas). Then I started it again after 5 minutes, slowly drove home and it was nothing. And now the question: what can that be. Thanks already for your help mfg