Random post order and taxonomy filter

Better to use get_posts. This is how you can use “rand”

<?php
$args = array( 'orderby' => 'rand' );
$rand_posts = get_posts( $args );
foreach ( $rand_posts as $post ) : 
    setup_postdata( $post ); ?>
    <!-- Do the things here... -->
<?php endforeach; 
wp_reset_postdata(); 
?>