Re-reading the original post, I don't get the sense that he's expressing fear. Agitation yes, and perhaps a revulsion, or tension, or anger but it's hard to say from just his saying he feels his blood pressure rising, losing his calm and disliking the feeling.
I don't know if that's normal or not, and I don't feel it, but all of those strike me as reasonable reactions to driving in traffic. People could randomly damage your interests, your health and well-being, or worse, and you are relying on their judgement and skills to prevent that. A certain amount of apprehension is more logical than the sanguine confidence we generally have, and speaking personally I've always felt that this was a kind of cultural blind spot that most all of us suffered, including me.
And I do see a lot of drivers who appear to be agitated, judging from their expression and behavior, so I think the OP is more reflective of honesty than of a psychological syndrome.