shortcode_loop.php

<?php
function productos_nuevos_shortcode() {
    $args = array(
        'post_type'      => 'product',
	'posts_per_page' => -1,
    	'orderby'   	 => 'menu_order',
        'meta_key'       => 'nuevo',
        'meta_value'     => '1'
    );
    $loop = new WP_Query( $args );
    if ( $loop->have_posts() ) {
    	echo '<div class="woocommerce columns-4"><ul class="products columns-4">';
        while ( $loop->have_posts() ) : $loop->the_post();
            wc_get_template_part( 'content', 'product' );
    	endwhile;
		echo '</ul></div>';
    } else {
        echo __( 'No products found' );
    }
    wp_reset_postdata();
}

add_shortcode('productos_nuevos', 'productos_nuevos_shortcode');
?>