I created a template and then duplicated it for each page. The client didn’t want the site in a CMS, especially not WordPress. Each template calls and include for the Header.
<?php include('Includes/Header.php')?>
It is using the same Header each time so I didn’t think that it would cause it to reload the header each time, but I think that may be the cause.
I don’t see a flash in Chrome PC either. Maybe you have a slow connection?
The only thing I can think of is the font awesome icons may cause a delay while they are loading. Added fonts always cause a flash as they load later. Comment our the link to the font file and re-test. It probably won’t make a difference though.
Another (more complex) way to check is to make a testing version of the home page and then you can strip out elements one by one and check if you can spot the cause.