default-woocommerce-ordering.php

<?php

add_filter( 'woocommerce_default_catalog_orderby', 'musilda_default_random_order' );
function musilda_default_random_order(){
  return 'rand';
}

add_filter( 'woocommerce_default_catalog_orderby', 'musilda_default_price_order' );
function musilda_default_price_order(){
  return array( 'price', 'ASC' );
}