Before you even begin the very short rides like Sherryvic suggests, you should just let your dog hop into the car and sit in it for a few minutes while it's in the driveway. Don't even turn the engine on! Gradually increase the time he sits in the car with you, and give a treat for good behavior when you both get out. Then have him sitting in the car with the engine going (but not moving), increase the time gradually, and give a treat when he's been good afterwards. This should get him used to just being in the car uneventfully, and praise/treats for sitting nicely should encourage him not to be nervous or spastic. Then try the short little trips around the block, etc.

Good luck! We love travelling with our own dogs, and they dig it too!