Sex in car 🚗😱

Hey everyone!☺️ please help!!😨 my boyfriends wants to have sex in car and I'm so terrified! I've never done it outside of the bed ( on couch or floor counts the same haha )... I definitely want to try it but I'm very insecure and I don't know what position we could possibly try there. Will we even fit in the back of the car?! I have no idea... Do you have experience in this area? Please tell me how it went and some Tips if possible🙈 thank you 💕