Hi IDM,
Well it's the "getting stronger and stronger" bit that's standing out to me, and I know things have been real tough for you in the past

........I'd be trying my best to persuade you to get a car
without a sunroof

, but guessing other fantasies might replace it then..........??
I'd say that with depression that inner sense of/instinct towards self preservation or self protection can
definitely sink........and sometimes consequences..........well you're not going to care about them quite as much, right??
One possibility in the
short term though might be finding a
safe way to channel the impulses to do something "risky"..........all that's coming to mind right now is amusement rides or sports sorry..........but
something 
And maybe have a safety plan for while you're in the car if the impulses strike e.g. going a route that's going to allow you breaks maybe for a drink if the impulses are strong........, deciding a point in the impulses where you're going to pull over and take a bit of a walk........if there's any music that might help "take your mind of them" then playing that..........things like that............And longer term...........well got to be about working on where those impulses are coming from, I'd say.It might be "simply" depression related, and I know you're working on/through that

But there might be some aspects of it
still that you could pinpoint..........like feeling a lack of control, feeling restrained day-to-day...........that you could do things day-to-day to counteract...........
Could be you're feeling that you don't matter

, and it doesn't matter what happens to you.......but I,
for one (and I'm sure other people on here too) as I'm sure you'll know

am not going to give up on trying to convince you that YOU DO!!!

So........maybe talking to us..........talking to your T..........to work through the "Why"'s???
But try to keep safe, hey IDM??
Alison