Phone hanged and Screen turn off by itself now not turning ON.

Hi there,

Recently I get to know that my I phone 12 PRO 128GB starts hanging while capturing videos, photos etc. it gets hanged and restart by itself. But 1 week ago after opening an Messenger app I tried to reply to a particular massage when the keypad come up to type massage phone gets hanged and then turn off completely not turn on till today. please help how to repair the same. what could be the issue with it.