when u put the clutch in and shift the gear u have to let the clutch go slow and give it a little gas just like on take off. if you let the clutch out fast without giving it gas then it will jerk
It could also mean that the car has a built tranny, dont always assume the worst. Check your fluid, and get a flush and filter change, if the problem still exists. Then take it to a mechanic.
It means you need to have your car's transmission looked at by a certified mechanic immediately. If you let it keep getting worse, you may be in need of a new transmission soon.
Is this a standard? You could be popping the clutch. If it's a newer car, it could be a computer problem....You haven't given us a lot of detail though.