Why my car jerks when decelerating or cruising in slow speed?

Your car jerks when slowing down because the transmission is having trouble shifting gears. This usually happens when the transmission fluid is low or dirty. When the transmission fluid is low, it can't properly lubricate the gears, causing them to grind and jerk when they shift. If the transmission fluid is dirty, it can cause the same problem. To fix this, you'll need to add more transmission fluid and/or have the transmission flushed and filled. You may also need to have the transmission filters replaced. If your car is still jerking after adding more fluid or having the transmission flushed and filled, there's likely a more severe problem with the transmission. You'll need to take it to a mechanic to have it checked out and repaired.