The screen of my iPhone 6 stops working at random times. In fact, it doesn't work more than it does work. It will also click on random buttons which makes it hard to use any apps because it will randomly click on something. My phone has no water damage and is not cracked. It's been doing this for a few months now
If you're near an Apple Store visit them so they can take a look at it. As long as there is no damage that would void the warranty they will repair it. If you can't access a store contact them to iniate warranty repair/replacement. You can also go through Verizon but I would do that only if you can't go through Verizon.