https://www.theverge.com/2017/8/18/16169428/google-autoplay-video-previews-on-mobile-android

The next time a video shows up at the top of your Google search results, it might start playing automatically — fortunately, with the sound muted.

Google is beginning to add what it calls “video previews” to search results. They’ll start out on Android, where they’ll appear for searches made in Chrome and the Google app. At first, they’ll only be in English and in the US, but Google plans to expand the feature globally and in all languages in the future. A spokesperson says Google also hopes to expand video previews to other platforms, so presumably iOS and perhaps the desktop are coming.