I don’t think there is enough space…
It sounds to me like an automatic reaction to a threat. Like when someone sneaks up on someone, and they punch them. In that small moment, they felt threatened and instinctively responded.
I could argue that the OP wouldn’t have processed it as a car, but just big thing threatening you and reacted without thinking. Is that self-defense?
A lot of people seem to use the phrase that way.