Is there any kind of device or support that i can wear to help with vibrations and bumps like in the car for the shoulder to keep it more stable?

Shoulder Sling: A shoulder sling would stabilize the arm and shoulder and is even used for arm fractures.

Probably not...: It all depends on what the cause of the shoulder pain and instability is. If you have an unstable shoulder there is something called a sully brace that can be worn, but other than that, any other brace that would hold your arm still you could not wear while you were driving (if you were the driver). There are also some neoprene wraps that can be put on the shoulder to help, but not for stability.