Sick, scared, or both
Car sickness and car anxiety can look alike. Dogs who are nauseated may drool, lick their lips, yawn, swallow a lot, whine, or vomit. Dogs who are afraid may pant, pace, shake, try to hide or bolt for the door. Many dogs have both, since feeling sick in the car teaches the dog to fear the car.
Puppies often have more motion sickness because the inner ear is still developing, and many grow out of it. Adult dogs can develop it too. Always talk to your vet first. Your vet can rule out other causes and discuss options for nausea. We cannot recommend medication, but we can tell you what your vet might hear from you: when it started, how long the drive is, what happens, and what you have tried.
Also think about what the car means. For many dogs it is the vehicle for the vet, the groomer or boarding. If every trip ends in something stressful, no wonder the dog is nervous. See making vet visits easier.