"Many people love to take their dog on errands and fun adventures in the car. Some even take their cats. Some dogs and cats become anxious in the car with others refusing to enter the car at all. What can we do?
Anxiety in the car is a common behavior among both dogs and cats. There are many different reasons for this including movement of the car, car noises, or sights and sounds outside the window."

https://veterinarypartner.vin.com/doc/?id=10052310