[_dain_]

>For example, when my car is at the garage I feel like I'm going through a kind of drug withdrawal. It really bothers that I can't just jump in my car and go somewhere and instead I now need to catch a bus or walk. Before having a car this would have been normal to me, but am I now addicted to my car or is it more that having a car is really convenient and now I'm experience the inconvenience of not having access to one?

"Addiction" is probably not the right way of framing it, since it applies more to the place you live rather than some aspect of your character. The place you live may be car-dependent, if walking/cycling/public transport are not adequate substitutes even temporarily.