My Iphone 5s is having problems completely out of the blue?

My phone screen doesn't work. Everything looks fine and I still get my notifications but when I try to unlock my phone by typing in my password or something then it doesn't do anything. The only thing that works is the drop down menu and the bottom menu. And when I use siri the screen works perfectly fine and I can scroll up and down but I can't select anything still.

Press the lock and home button at the same time and hold for a few seconds til the whole screen goes black. It'll restart. The same thing has happened to me a couple of times. I have no idea why this happened, my guess is that I have too much stuff on my phone, the memory is always 'almost full' lol, but this hasn't happened in a long time.
Hope this helps