Do a "safe mode" boot.
I had to do that with mine for something and it actually helped.
So with your phone, shut it off. When you turn it back on, have your finger on the volume down button and on the home button when the first Samsung comes up. Hold until you see the SAFE MODE on your screen. What this does is if you have something interfering with something for it to not be able to work, it will work here. So it can be something on your phone that you may have on there.