Put your Android Tv on suspension automatically within x minutes. Most Set-Box Android have no automatic shutdown function. With this App pick a time for the off and Android TV will enter into Suspension mode.
If you don't activate the device or just your device doesn't leave:
Go to Adjustments->
Device preferences->
Safety screens->

Select Shooter Switch start in five minutes and put to sleep in 30 minutes.

You can sleep quietly while you watch your favorite videos the device will rest at any time you choose.