iPhone 6S screen turns black randomly

I recently got an iPhone 6S, and it’s been working for about a week, until the screen started randomly going black today. But after it goes black, I can turn it back on and use it for a while, then it happens again. I noticed that this issue didn’t happen before I updated to iOS 13.3, and I assured that it wasn’t the power button getting pressed by itself. I have been using the phone very carefully so it doesn’t have any issues, so I don’t think I really “broke” it. Also, it’s not one specific app that’s causing this, because it has happened in the News app and the Safari app at this time of writing, and I hope you can help stop this from happening to even more apps. This is the second time in the past two months that I have had issues with any type of iPhone. Please help me fix this. Thank you.

(EDIT: I just noticed that this issue happens the most when Low Power Mode is turned on. Do you know why?)