I had a similar problem before, did all the restoration etc. I eventually took it to the apple store they said it could be the screen but could also be other issues. Their policy was to charge for a replacement screen but to give a brand new phone. The phone was a year and a half old and 3 mobile refunded the cost.
My new phone has now started to do the same thing. It seems to coincide with the latest software download so I am wondering if that could be part of the issue.