Phone not turning on

I woke up one morning and I try to turn on my phone which does not work. During the night it was on "Do not disturb" and also the brightness was turned all the way down. It was also charging. I hold down the power button but still nothing works. I also tried that with the home button. When I held down the home button siri turned on, so I knew that it was still on. I just couldn't see the screen. I leave it alone for 8 hours and don't touch it (it's still in the charger) and I come back with the same problem. Anyone got any tips?