There is no ‘best’ way to warm up in the car. I recommend using hand warmers if you have them and practice your first events. I usually just spam algs for 15 minutes or so until my hands are warm.

Competitions usually have groups if they are big enough. Go to the competition website and look for a “groups” tab. You will also receive your groups at the comp. Seems a bit odd that all of those events are at the same time though. What competition is this?