Volvo S80 jerking when stopping and starting

Help! I have a 2005, Volvo S80, it has 107,500 miles on it. In the last two months the car has started (NOT everytime I drive but sometimes and then the next time I drive it it is fine), jerking and sometimes a thunk sound as it jerks. When it is doing it it does it s I finish stopping from going fast or slowly AND then when I accelerate it feels like a the car has a delay from the gas pedal. And starts with a jerk and the thunk sound. When I brake what happens make me imagine that the wheelbase has stopped and the the body of the car is still going and clunks as it stops too. Like it is lurching over the wheel base. Sometimes it does it the whole time I am driving (starting and stopping) and other times the car drives fine. Talking to several mechanic they all seemed stumped and have never heard. But mechanic guesses that they want to fix have been electrical board shorting, timing belt, transmission needing to be flushed. Does anyone have any idea what this actually is? And what needs to be done about it. Like I said before HELP!

Has anybody bothered to check the motor mounts and the transmission mounts?

As to transmission flushing…
When was the last time that you had the trans fluid and filter changed?
Even if it has nothing to do with resolving the “jerking” problem, failure to attend to that vital maintenance is going to result in a HUGE repair bill in the near future.

Transmission service should be done every 3 years or 30k miles, so your car should have had this service performed 3 times so far, with a 4th service coming up in the next year or so.

It seems the torque converter is the problem. The computer tells the torque converter what to do based on sensors things like vehicle speed and throttle position. I feel you need a Volvo dealer, a Volvo specific mechanic, or a foreign car specific transmission shop.

Don’t put this off. That jerking is putting huge stresses on fragile parts.