2003 CR-V starting problem

I have a 2003 CR-V and it sometimes has problems starting. After it has sat out in the sun for a while you will turn the key on (radio & dash lights work fine) and try to crank the engine but it does not do anything. If you turn the key all the way and try starting again it usually turns over after three or four tries and starts up fine. When it finally does turn over it isn't slow and starts just like nothing happened. I took it to the auto store and no error codes are showing up. I can't get the problem to repeat enough that I can take it to a mechanic (it happens about once a week). Any ideas what might be wrong and how I might be able to isolate it?
Thanks,
Nick