Since 3.6 WordPress has included MediaElement.js in core. As an example, if you take a look at the video player on the http://mediaelementjs.com homepage you will see that for a portion of the very first second, the player looks slightly different. It seems the styles take about 1 second to load.
Does anyone have an idea why there is a slight delay for the styles to "kick-in"? the video player looks crude/ugly to start with (for roughly 0.5 seconds) - so I would be grateful for any help in understanding why the player looks different to start with.
I am unable to reproduce your issue (see it now, really quick for me in chrome only). Have you tried forcing the scripts / css to load in advance of the page?
I have done similar to this with a different problem (likely same root cause). Also had to cache the CSS to make it work: http://www.phpied.com/the-art-and-craft-of-postload-preloads/
I got this from a SO thread but only bookmarked the blog post - found it: Force browsers load CSS before showing the page