My phone won't turn on. Help!

Yesterday, My phone was working perfectly. Then this morning when I first woke up my screen was on but it was the dark gray color as if it has just powered off. I decided that I would push the power button cause it wasn't going away. Then I went back to sleep. I wake up and I push the power button to turn it on. And it won't please help.

'P.s. My phone was on the charger the entire time.