No Start Issue

Probably not it but check your timing. I had a thread going a while back with an issue where I could intermittently get the engine to fire up with the key but normally it would slow crank. If I jumped the starter relay, it always cranked over fast. Turns out my timing was too advanced. Backed it down and the problem went away thanks to the experts here.

I know you say it only happens when the engine is warm but there is a slight chance that it's a coincidence. Wouldn't hurt to check, plus it's free.