OK, this is a new issue for me. I looked around and didn't find another thread with this issue. A couple of days ago, when starting a race in single player mode. I started getting put in the first car on the list of racers in the opening screen. I do my usual check the car setup screen because the game doesn't always save my setups. And the first time a click the race button, I'm in the first car on the racers list, not my car. So I go back to the garage and click race again and I'm in my car this time. It only happens at the very first of the game. weather it's practice of qualify doesn't seem to matter. And as I said only on the first time I try to go out on the track.
Change the amount of visible cars in video settings to 24 or so and that should fix you up. You can also press the enter key on the numpad (I think) and that will put you back to your car