NTA It's a bit of a tricky one but you're not alone, I used to see my Dad snap at my mum a lot whilst driving and always thought he was a dickhead.

Fast forward to my driving years and I've snapped at every girlfriend I've had in the car at least once. I've come to the conclusion that's it's not the females fault as they are just chatting/messing and forget that you are having to concentrate a bit on the road and I don't think it's the males fault either as it's often a very unthought snap that seems to pretty much come out of nowhere.

I do have my father's temper though and my girlfriend understands that and I struggle a lot to not be a miserable snappy cunt like him and take it all out on my partner like he did my mum. As most of the time I do manage to stay mostly on top of it though my girlfriend forgives me when I do snap, I try to apologise almost as soon as it happens now as I don't mean to do it it just comes out like loud word vomit.

For some advice though, I'd sit with her and explain how driving can be a stressful time for you again but really explain and tell her that you don't mean it but if she does certain things in the car it's going to cause reactions like that.