That is the torque converter taking up the slack that occurs between disengaged to engaged. The difference between sitting idle and 'let's go'
Check the mounting of the gear box, because the mounting of the gear box is like shock absorb.
have your transmission checked sometimes torque converter clutch isn t locking or unlocking properly
If it's an automatic, your transmission may be dying; if you drive a manual, you're probably letting the clutch out too fast.
You could have ignition problems if it is the engine causing the jerk.
Poor driver or bad transmission.
change the map sensor
you may not be at a high enough rpm
rpm too low maybe you are shifting to soon
it jerks because if it is automatic it is goin down a gear
ur senses
you are going too slow for that gear your engine has very little torque at low rpm
igniter is possibility