2001 Mitsubishi Eclipse starter

Last summer I had 3 starters (rebuilds) replaced in a mater of 2 months. This is when it was summer and the weather is hot. Now we have had our first hot spell and again after I have drove around town and made 4 or more stops I turn the key and the motor does nothing. Some times if I trun the key and hold it on it hesitates and then starts. Samething as it did last summer and they said it was the starters.I wait for the motor to cool and it start right up. Is this the starter again and why does it only do this when the weather gets hot. It ran fine all winter.