HTML5 Video Autoplay not working correctly

Question

I want the video to automatically play, but it doesn't when the page loads. Because the video consistently stops after two seconds when I hover over it to reveal controls, it appears to be a buffering problem.

I just returned to the website and autoplay appeared to be working, but when I try again, the same problem persists. Could this be a buffering issue? What can I do to stop this?