In reply to higherclimbingwales: Never quite that long, but always find the first 3k of any event hard. As others have said, it helps to have a good warm up - for anything 5k or less that matters it will be an over-distance steady warm up finishing with a few sets of strides, to just get your legs feeling springy.
Even then to some extent I still suffer it - I can't explode off the line in the same way some friends do, but the difference between the pace ultimately achieved and the initial pace for similar effort is smaller if I'm well warmed up.