When a car jerks when stopped, it can be caused by a number of issues. Some of these issues can be resolved by simply topping off the transmission fluid, while others may require more extensive diagnostics and repair services. Some of the most common causes of this problem are low transmission fluid or a dirty transmission filter. If this is the case, simply replacing these components should fix the issue.
Another possible cause of this issue is a failing torque converter. The torque converter is responsible for boosting the engine's performance and can cause your car to jerk when stopped if it fails. This can be a more serious problem, and may require the replacement of the entire transmission.
A damaged spark plug may also cause your car to jerk when stopped. The spark plugs create a spark during the combustion process, and if they are damaged or fouled, they will not be able to properly ignite the fuel. This can lead to engine misfires, which will cause your car to jerk when stopped.
Other common reasons why your car may jerk when stopped include a faulty ignition coil, a damaged mass airflow sensor (MAF), dirty fuel injectors, or a bad catalytic converter. Some of these issues can be fixed by replacing the ignition coils, fixing the throttle position sensor, cleaning the MAF sensor, changing the air and fuel filters, and replacing the spark plugs. If the jerking persists, you should contact an experienced professional to perform a thorough diagnosis and repair.