Double check your settings because there are 3 that can be turned off.
Settings -> iTunes & App Store -> 1) Music 2) Apps 3) *Updates* .
Are you plugged in/charging and internet connection enabled? Those 2 conditions will cause an automatic download of a Safari update for malware sites and an OS update if it's available.
Right. You're misunderstanding what those options do.
The music/apps/books options automatically download the music/apps/books downloaded on your other iOS devices. The updates option automatically downloads app updates.
None of the options refer to iOS updates unless the option to automatically download app updates includes iOS updates, but there's nothing to indicate that it does.
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Just an update, I restored my iPad as a new device and set it up from scratch and it's running great now