How to Autoplay Videos on YouTube
The Autoplay feature on YouTube makes it easier to decide what to watch next. After you watch a YouTube video, we’ll automatically play another related video based on your viewing history.
To prevent long Autoplay sessions, keep in mind that:
If you're connected to a mobile network and have been inactive for 30 minutes, Autoplay won't start.
If you're on Wi-Fi, Autoplay will stop automatically after 4 hours.
To learn more, please visit the YouTube Help Center: / help