The only period during which I felt as confident getting into an aircraft as I do when driving a car was when I was flying as regularly as I drive, ie for the year or so during which I was a full time instructor. Otherwise I never have, or have had, quite the same level of confidence. And I have well over 1000 flying hours. And in my experience that's true of many pilots, if not most.
As various people have said, a lot of this is because flying is simply not like driving, in that you can't just pull over to the side of the sky and phone the AA. You have to be capable of dealing with everything, in some way or another. If the engine plays up in your car, you stop. If it fails in an aircraft, you have to deal with it. If you're trying to drive in a very busy city environment and feel it's all a bit much, you pull over, put on the hazard lights, and take a couple of deep breaths. It's hard to do the equivalent when going into a crowded airport.
When you get your licence, you may well not feel confident doing a lot of things. So make haste slowly. Never be afraid to take an instructor with you, or a more experienced pilot friend. Gain experience, but slowly. If you want to extend yourself, do ONE new thing per flight, ie either go to a big airfield, or fly in challenging (for you) weather, or take a non-flying passenger, but not all three at once.
I'm sure when you first got your driving licence you weren't that confident either, so as you did then, give yourself time.