iCloud Bach up
I have an iPhone pro max, it does not automatically back up iCloud, it be charging, connected to WiFi, and home screen is locked, my iPhone X would automatically back up every nite, thanks
iPhone 11 Pro Max, iOS 13
So..What's your question? Do you want to make it so that it automatically backs-up your iPhone?
If so, read this: Back up iPhone - Apple Support
If that did not answer your question, try to turn off iCloud backup and turn it back on.
If you are still experiencing issues, contact Apple Support :Contact Apple Support
Best of luck,
Mac