Daughter’s iPhone won’t turn on

For the past week, my daughters phone has been randomly turning off. We looked it up and we force restarted it. It’s ben turning off a lot, so she had to restart it many times. Last night it turned off, and she tried to force restart it and it didn’t work. And it still hasn’t worked since last night. It’s just frozen on the screen with the Apple logo. How do I fix this?