Every couple of weeks, I have a hard time starting my Jeep. I can flip the key on/off several times or even leave the key on for 30 seconds and nothing helps it. Once it finally does start, it runs rough for several minutes. If I immediately take off, it runs fine until you drop the RPMs down to shift gears then it stumbles. I also have noticed that the days this happens, my temp gauge stays on 100. While driving down the road, I can hold it to the floor in 3rd and my temp comes up to normal then drops back down to 100. Any ideas????