<video id="video" onloadstart="this.volume=0.1" loop="" autoplay="">
<source src="" type="video/mp4">
</video>

<script>

var videoArray = [
'video1.mp4',
'video2.mp4',
'video3.mp4'
];
var count = Math.floor(Math.random() * videoArray.length);
document.getElementsByTagName('source')[0].src = 'video/' + videoArray[count];  //путь к видео
var video = document.getElementById('video'); // Это id="video"
video.load();
video.play();
</script>