How to fix a blank white screen on an iPhone 4?

I have an iPhone 4 that I think got too hot when it was left in the car during a baseball game. If I press the lock button the screen will flash on for about 15 seconds but it's just a blank white screen, then it goes black again. I've tried resetting it and even taking the back off and unplugging the battery from the phone. I've seen many videos that say how to fix a blank white screen, but none of them seem to pertain to what's going on with my phone. Any help would be appreciated.

Hold the top and home screen button down at the same time until it shuts off. If that doesn't work either then that means the wires were fried in the heat. I had that problem too I put my iPhone on the dash of my car in the heat and 5 minutes later it said "I phone is too hot"but the screen never turned white.