98 Deville, 106k, no codes

Start the car and put in reverse, car behaves either like the transmission is slipplng for a second or a spark plug is misfiring, it is hard to describe but the car jerks for a second or two. After that, no issues for 10-15 seconds before it jerks again one or two times. Same behavior in drive one or two sputters, then no problems in 2nd and 3rd gear. 4th gear is fine at high rpm's, but when it drops down right before shifting down to 3rd it tends to jerk. At the stop light, it sputters before I take off, fine after that. This behavior is so intermittent and sporadic that I took it twice to my mechanic and both times the car ran great and he could not troubleshoot it.
Having the AC on seems to increase the frequency and the intensity of the jerking.
What do you guys recommend? I would like to bring it back to my mechanic pointing him in the right direction.

Thank you

 

I have a 1991 Cadillac DeVille I've had a ton of work done on it I got so many new parts on it it's ridiculous what it's doing now is it will run great and then all of a sudden it starts misfiring and choking and if I turn it off turn it back on it runs great again and then it'll start all over again misfiring and choking nobody seems to know what is wrong with this car.

I need some help from you guyz.