Found this while playing on Facebook.
iPhone Slowing Down
Today my iPhone got stuck. I went to unlock it and it took what seemed like minutes to respond. I had voicemail but after fifteen minutes of waiting I gave up.
The solution was simple. The iPhone just needed a quick reboot. I held down the power button for about five seconds and then slid the block to shut down. After I turned it back on my iPhone sprang back to life.