Truck wont start when warm?

Was heading home today from work (yeah we mazdabsceners do work), stopped at a gas station and got a drink, hopped back into truck and tried to turn it over, it did nothing. I know its not the battery cables or battery itself due to the fact I swapped these out about 2 and a half months ago. So I called a tow truck and waited around, about an hour and a half later I decided to see if it would turn over, and it turned out like its supposed to, and I drove home. Got home and decided to see if it would start again. It didnt. Any ideas? Im actually baffled about this one, truck is always giving me problems but the fixes are obvious.

I've had that happen on a few cars, and it's always the starter going out, and won't work when it gets heat soaked from the engine running. I'm not sure what part of the starter, maybe just the solenoid? I always just replace the whole thing.