Q: iPhone 5 iOS 9 troubles with installation

I have an iPhone 5 and I am stuck on the "slide to upgrade" screen. When I slide and then punch in my passcode, I get a white background with a black apple symbol on it with a loading bar underneath. The loading bar gets to about a third before the screen reverts to the "slide to upgrade" screen. Sometimes there will be a box appear on the screen that says "zoom enabled" which is weird. iTunes will recognize the phone, it will first ask if I want to allow this computer to access information on "my iphone" to which I click agree. Then it says "to allow access, please respond to your iPhone." When I slide to upgrade on my iPhone, the usual happens. Has anyone else had this problem? and if so, what do you do to fix it?