You can use pre_get_posts to set random ordering to your taxonomy pages. Just note, random ordering duplicates posts between paged pages as each page is a new query and not an extension to one. This is unfortunately how random ordering works.
You can try the following
add_action( 'pre_get_posts', function ( $q )
if ( !is_admin() // Only targets the front end
&& $q->is_main_query() // Only targets the main query
&& $q->is_tax( 'product-category' ) // Only targets the product-category tax pages
$q->set( 'orderby', 'rand' );
Asked in February 2016Viewed 1,945 timesVoted 4Answered 2 times