Why does my screen continue to go unresponsive?

Yesterday I tried to updating my iphone on iTunes it took hours ( my computer is very slow ) so I feel asleep with it on the computer. In the morning I woke up and iTunes was deleted on my computer my phone wasn't done downloading. And off and on today my screen has been going unresponsive a lot. Only the home power and volume buttons work. I tried reseating it's and rebooting it. I don't know what else to do it's make my phone go slow and jumpy and continues to freezes. PLEASE HELP

THANK YOU