1999 Ford Taurus SE won't start when warm

one 'guess' would be starter expanding from heat of engine than sticking till it cools off, than unsticking as it cools off. one way to test it is take a jug of cold water with you then when it happens pour the cold water on the starter to cool off and see if it works. another 'guess' is a temp sensor that is reading the engine to hot, than when temp drops it allows it to start. a good analyzer will tell what the temp sensor is reading. many times you cant find out what it is unless you test during the condition, which is why when you take it to the mechanic the condition doesnt exist. take the car to him and have him run it till it creates the condition. in any case i think something is being affected by heat...but than what do i know, lol!