I have made a car. I have seperate collision groups for the body and the wheels so that they dont collide with each other. the car is working perfectly fine but when i get into the car it jerks and the wheels and springs go to random places and get kinda stuck and the car bounces and jerks. even when i collide with a wall or a slightly big block it does the same and then becomes normal after few seconds. it is working smoothly on plane and inclined surfaces. I have shown it in video below.
I solved the problem. For anyone having the same problem, when the player sits in the car loop through all the parts and meshes in the character and make them massless. also change the collision group to something that doesnt collide with the wheels like the group of the car body. That fixed it for me.