Video on Mobile

I uploaded a mp4 video file using the “video” option within Media Elements. Looks great on my computer but is only showing a “play” button on mobile – no initial image.

For my other website, when I add a video using a Vimeo url, it displays properly (with initial image) everywhere.

Is there anyway to get a manually uploaded video looking as good as a Vimeo video – on mobile?

Thanks!