Competition warm-up

Hi,​I have been climbing for 15 years. Also I love comps, and while I am on the stronger spectrum of climbers in our usual comps, sometimes I make finals, but most of the times I don't.Not because I couldn't have climbed the necessary problems required for finals, but because shortly after the comp starts I get a flash pump. And this flash pump persists way longer than the actual given climbing time.I am referring to relaxed jam type qualifications, where you have like 20 boulders to climb, from easy to hard.​How should I warm up in order to not get pumped early in on such a bouldering comp?Please help, it is really frustrating...Thank youuu!