I powered off my iPhone (sample instructions). I see the progress wheel for a few seconds after holding down the power button and sliding the 'slide to power off' and then I see the silver Apple logo as if it powered on immediately.
Is this a reset and not a power off? Did this before going to sleep and woke up with a dead battery.
I've struggled with low battery life and did the full replacment of operating system. If I have to go through that again, I'll get a new phone.