I've just get now the same issue with my video
<video preload="none" autoplay="autoplay" loop="loop">
<source src="Home_Teaser.mp4" type="video/mp4">
<source src="Home_Teaser" type="video/webm">
<source src="Home_Teaser.ogv" type="video/ogg">
</video>
After search, I've found a solution:
If I set "preload" attributes to "true" the video start normally