There are few ways to turn on a phone with a broken power button, unless you're willing to work to get your hands dirty with developer settings.

How to Force Restart an Android Phone Without a Power Button If your Android phone’s power button is broken or not working, you can still force restart it using the following methods: ...

Your Android phone can sometimes go haywire unexpectedly. In this case, it's important to restart your device to assess the potential issue that led to its shutdown. You can switch it off and on to ...