Most mobile devices will not autoplay a video.  To force them to do so, do the following:

1. You must have an embedded iframe like below and the class "iframe-container" AND the div with the id "player". The "playlist" attribute on the iframe must be present for looping to work.  Replace the video number in ""https://www.youtube.com/embed/RaEQCqMt424" AND in the playlist attribute with the youtube video number you want to embed.

<div class="iframe-container">
    <div id="player"><iframe width="560" height="315" src="https://www.youtube.com/embed/RaEQCqMt424?autoplay=1&amp;controls=0&amp;ampshowinfo=0&amp;loop=1&amp;mute=1&amp;playlist=RaEQCqMt424" allow="accelerometer; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen="">
        </iframe>
    </div>
</div>

<!-- 1. Note that the <iframe> (video player) will replace this <div> tag you've already put in in #1 above. 
<div class="iframe-container">
<div id="player"></div>
</div>
-->

2. Insert this script in the page or in your js/script.js file.  Be sure to replace YOUR_VIDEO_ID with your youtube video ID AND also replace it in the playerVArs > 'playlist' variable below:

<script>
    // 2. This code loads the IFrame Player API code asynchronously.
    var tag = document.createElement('script');

    tag.src = "https://www.youtube.com/iframe_api";
    var firstScriptTag = document.getElementsByTagName('script')[0];
    firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

    // 3. This function creates an <iframe> (and YouTube player)
    //    after the API code downloads.
    var player;
    function onYouTubeIframeAPIReady() {
        player = new YT.Player('player', {
            width: '100%',
            videoId: 'YOUR_VIDEO_ID',
            //replace above
            playerVars: { 'autoplay': 1, 'playsinline': 1, 'loop':1, 'mute': 1, 'playlist': 'RaEQCqMt424', 'controls':0},
            //repace RaEQCqMt424"RaEQCqMt424" above with your youtube video id
            events: {
                'onReady': onPlayerReady
            }
        });
    }

    // 4. The API will call this function when the video player is ready.
    function onPlayerReady(event) {
        event.target.mute();
        event.target.playVideo();
    }
</script>