Phone will not turn on/unexpected shut down
My phone was on and working 30 minutes ago., Then it would not show my lockscreen but was a black screen that still showed the time and notifications. All of a sudden, it stopped working. It has been charging for more than 15 minutes ago and I followed the steps online. I pressed the volume up then volume down and held the power button but nothing happened. What do I do?
iPhone 14 Pro