2001 Chevy Lumina car fail to start when engine is hot abou

I have Chevrolet Lumina LS 2001 model and it has done 180000km, from past few month I have notice, when I drive the car for few km and engine hot about half way on temperature dial, and if I stop the engine for few minutes at signal, and try to restart the car, some time it take longer time to start the engine and some time the engine fails to turn, and I hear one or two click sound. But if I wait for few more minutes, by that time engines cools down, and the car starts very easily. I take car to check battery and found the battery is ok and cleaned the battery terminal. Still I face these problems. So I avoid switching off the engine for short span, at traffic signals etc. Please advice me what could be the problem. Some time I feel engine getting jam when it is hot, due this it not starting.