Car won't start whenEngines hot

After driving the car (Mazda MPV) for 15 or so minutes and turn t off, it won't restart for at least 30 minutes. When you try to turn it on, it will only turn over once, each time you try.
Waters, oil, points, battery, distributor, starter, are ok.
When it finally does start, it's like there was nothing wrong with it, it fires up straight away and drives well.
We're in San Diego, and thinking back it didn't seem to be a problem during winter, but the summer heat seems to affect it again.