Motor Question

[RWole]

I was thinking vapor lock due to the heat.
The motor ran well all year and in the morning.
It began to act up aroung noon(high temps.)
What baffled me was if I let the motor sit for
about ten minutes it was fine until it ran for a while.
I drove home (45 minutes) and ran it it the driveway
and it started up and did not stall. Not even a flutter.
Smooth as can be.