Could be that the version of iPad you are testing it on doesn’t like the codec of your video. My iPad played the video consistently every time I refreshed the page.
If you want to use an image or other element to play the video you can use some pretty simple javascript to achieve this. The HTML5 video tag accepts the .play() method. I sometimes use onClick=’this.play();’ for some mobile devices. You could have an image overlay the video and use some basic js.
<img src='zzz' onClick"document.getElementById('your_video').play();this.style.display='none';" />
Abraham