Trouble with Temperature warning after ios 6 what to do?

I have an Iphone 3gs I upgraded to the IOS 6. After I did it this temperature warning came on and it was not even connected or anything. It has been almost 24 hours and it wont change. I rebooted and it did not change. When it comes on for a split second you can see the correct screen but then the temp. thing comes on . I downloaded the old 5.1.1 but when I connect it to the Itunes to follow instructions on how to do make it go back. Itunes will not recognize my iphone it shows the name and clicks off. The iphone basically cuts on and off every few seconds and I tunes will recognize it and then it was cut off.

What can I do? I do not have any idea how to get the iphone working again.