Mazda3 sporadically won't start after being driven
 

Hi there! We have a 2006 Mazda3 that has started to not start after being driven then sitting for a period like an hour or so. For instance I'll take it for a drive, half hour let's say. It will sit for an hour or two but then not start when we go to start it. This is a pattern I'm seeing. But let it sit for say 6 hours after driving, and it's fine, or overnight and it's fine. We've replaced fuel pump, starter and crank sensor. We are all stumped. Battery and connections are good. Just seems to be after we've driven it and go to leave after like an hour timeframe and it won't start again. Thoughts??