Rocky-shaky feel when accelerating

Recently had vehicle worked on in need of a major tune-up. Changed spark plugs. $300. 00. Less than two weeks later same rocky-shaky feel when accelerating car, sometimes while idle (car is automatic but perspectively it feels like a new driver learning to drive a stick shift and they stall, and the car abruptly jerks, then “stalls”). It feels like car is going to stall while in motion. Going from idle at zero mph in “D” and then driving just getting going up to even fifteen mph is rocky-shaky almost feels like gears are grinding! This is an automatic, I am not in four wheel drive but it feels like grinding. Anyways, after all of that descriptive detail, spark plug replacement, less than two weeks check engine flashing again, took car back in, cracked spark plug replaced. That was yesterday. Today, check engine flashing, yet again. I just do not get it. Suggestions?