I face this issue in Cyclocross as well. One way I try to mitigate it is to practice standing starts, usually outdoors so I can practice the pedal clip in. These intervals last about 30 seconds and I rest for a few minutes afterward, then go again. You can do this on your trainer, but I prefer doing the longer, slightly lower power intervals indoors. For those, you can do the typical VO2 max interval of 3-6 minutes at 120%-106% of FTP, with a few minutes rest in between.
The second thing is the warmup which @DaveWh mentioned. I do best when I have gotten a 15-20 min warmup and only had to stand around for <10 min waiting for the race to start. I also agree with Dave on the balance between going out fast and going out too fast, which will hurt you later in the race.
Oh yeah, try and get to the staging area early so that you can be on the front row.
Steve