First of all, how hot is hot. GM's electric fans do not turn on until 245 Degrees so anything up to that point is not really consedered too hot. Since you have had the car from new, has it always run as hot as it is now ? If not, did something change just prior to the problem starting, maybe a non related part being changed ? If so, maybe you should look at that.
Next, you say the car will not start for about an hour. Will the starter turn over and the motor just not fire and run ? If the starter is turning the motor over, then the next step is to go back to the three basic items that a motor needs to run, Compression, Fuel and Spark. I would assume that the compression is ok because once the motor does start it runs ok. So that leaves fuel and ignition. Have you checked fuel pressure during the time that the motor will not start ? Was it within GM's published specs ? Have you checked spark output at the same time ? Also within specs ? Are the injectors "firing" at the correct time or at all ?
If you have fuel, compression, and spark the motor should run !
Some of these tests are going to require some special equipment to do . Any up to date shop should have the equipment, and as long as the problem will occur for them, they should be able to track down the cause. If you need help finding a good shop check out this site: www.iatn.net
Now, if the starter is NOT turning the motor over, you have a completely different problem to troubleshoot. This could either be electrical, or something mechanical wrong with the starter.
Heat can affect many items on a car, both mechanical and electrical but I think if you do the above tests, while the car is in the "no-start" condition, you will find the problem.
Hope this helps,
Advanced Automotive Machine