Does your dog use a crate in the house? If so, place the crate in your car (if it will fit. If not, get a smaller crate) Then place the dog in the crate. Ignore it and clean the widows or sweep the floor. Then when the dog is quiet, let her out. repeat similiar until the dog will rest while in the crate in the car. Then drive to the end of the drive, and back up.
Get the idea? Baby steps, everything is done in stages. Most important is to ignore un wanted behavior. Only let the dog out, when it’s calm and quiet. Lenghten drives til it’s a normal activity for the dog. Once it will ride in the car in the crate. Try with just the pad from the crate. But make the dog lay down. Don’t let it roam around the car. if you have a glitch or relapse. Just go back to the last step where the dog was o.k.
Then take the dog in the car to a car dealer after hours. walk it around a few cars on a leash and let it sniff around. Then back in the car and home. After a few trips to the dealer. Go to a theater parking lot when the shows on. Hopefully a car or two will come by. Walk the dog on lead as before. Gradually, going to busier lots. Finally to streets with traffic. Odds are good that the dog will see that the car is o.k. pretty quickly. It will have everyones scent in it which should help. Use car rides to car lots as a bridge for the dogs understanding.
Goldendoodles and labradooles are a little on the exitable side. More excersise will help alot. Retrieving, and running beside a bike are good ideas. Mental as well as physical exercise. Are the thing. So, hiding things in the house that the dog retrieves. So, that it has to look around will pay big dividends.
Good luck.