I used to dissociate while driving too. It's really scary. I have several times driven somewhere and had no memory of how I got there, or ended up somewhere I didn't mean to go. It got so bad that I would get somewhere, not remember it, and then check the bumper of my car to make sure I didn't hit anything (or anyone!) on my way.
Then I found that if I sang while I was driving, for some reason, it kept me focused. So I have several different playlists of songs I know all or most of the words to, and I sing while I drive. I don't dissociate anymore as long as I am singing. Maybe give that a try? If that doesn't work, maybe something you can focus on, like a podcast or audiobook?
And definitely discuss this with you T. Maybe they can help you find a solution.