Create schedule to turn off iOS device every night..?
There is no feature for automatic turning off with no jailbreak.
However, you can:


Schedule "Do not disturb mode" and it will not turn you screen on to show useless notifications
Manually turn on "Low power mode" to stop all background processes and save your battery.
Plug it into a power source with no worries, since iOS 11.3 iPad has a new "iPad Charge Management Feature"