The automatic backup
should occur when the iPhone is...
- connected to power and...
- connected to WiFi and..
- is locked
All three conditions must be met for the backup to occur. The first things I would check are
- As obvious as it seems, be sure iCloud Backup is turned ON in settings.
- Do you have a reliable power connection? If your iPhone is charging overnight that would appear to eliminate that possibility.
- Check settings to be sure you have a WiFi connection. You might try disabling cellular data at night just to be sure you are forcing the internet connection to WiFi.
- Normally your iPhone would automatically lock itself after a set length of time, but try manually locking the phone, just to be sure and be sure there is not some app that either does not permit the phone to lock or even unlocks the phone to do its thing during the night.
- Try quitting any apps running in background. (If you double tap the home button and several windows show up those apps are in background. Swipe each of them off the top of the screen to completely shut them down.
