i am one who suffers from this badly. i, well atleast used to, totaly freak at the start, even before i'm on the way to the top of the track, one time i was ready to puke!
that just shows how nieve i was. i was mo0re interested in what others thought of my riding than what i thought of my riding, i still am to a degree, just not nearly as much. in my total of 5 races ever, i have leart a lot. i now think about, well, nothing really. im a little nervous, but concertrate on my breathing and heart rate, so i start the run relaxed and calm, with a good centre of balance.
last race (Batemans) i actually only arrived about 40 seconds before my run, so that was really rushy, and should have made me gone bezerk, but i calmly put on my helmet and gloves, and then just got into the right(ish) gear and then it was time to go. i did crap that run, but that was for a diferent reason.
so my summary of that huge bit of text about me (prob. mostly crap too) is that everyone will have their own way of doing things. obvious huh? i'd say just try thinking about your body and really focus on it, that way your body will be expecting orders. BUT, like i just said, do what works for you. try something different each race. you never know, simply thinking about which method to try might do the trick for you anyway!
sorry bout the long post, i tend to rable on a bit sometimes...