Autoplay can be enabled in the editor (Playback / Autoplay) or using variable autoplay:1, but it will only work on desktop computers. On all mobile platforms, full autoplay is prohibited.
Quote from iOS Developer Library
In Safari on iOS (for all devices, including iPad), where the user may be on a cellular network and be charged per data unit, preload and autoplay are disabled. No data is loaded until the user initiates it.
On Android, autorun is also disabled from version 4.1.
From iOS 10 autoplay for muted video is enabled, similarly it works with the version of Chrome 54 on Android, desktop Safari and TV. To enable this option, you must enable the
Desktop Safari from version 11 on Mac OS also blocks autoplay with sound.