Hard starting

My mazda 2 problem is difficult to start the engine. Ok, every morning I can start the engine as normal. No long crank. When the engine hot after driving for a long journey/time, I stopped the engine for a stopby or shopping, after 15minute + I want to start the engine, its takes long crank to start and its takes more than 5 second to start the engine. But when the engine stil hot after driving I stop the car less than 5minutes then I start back, its no problem. The engine can start faster. So what the problem?