OK, so you’re almost there. Let’s say you have this query:
$argsLoop = array(
'post_type' => 'cars',
'posts_per_page' => 12,
'paged' => 1,
'meta_key' => 'cars_price',
'orderby' => 'cars_price',
'order' => 'DESC'
);
$cars = new WP_Query( $argsLoop );
// All you have to add is this line:
shuffle( $cars->posts );
Now you can do standard loop and the selected cars will be showed in random order.