Are you using the original charger with your device?
Do you experience these symptoms if you test your device in safe mode? If your phone is misbehaving, it's possible that a third-party app is causing the issue. To figure out what app is acting funny, you can use the Safe Mode feature. In Safe Mode, your phone won't run any third-party apps. This allows you to easily identity and remove the app that may be causing the problem. Give this link a try to test your device in safe mode:
Thank you for that information. Have you had a software update to your device recently? Do you have a Bixby Routine set up on your device?
You're welcome. Please reach out if you need any assistance in the future.