Try this code.
<?php
if(isset($_POST['step_03'])) {
$que_01 = $_POST['que_01'];
$que_02 = $_POST['que_02'];
$que_03 = $_POST['que_03'];
$subcat = array("$que_01", "$que_02", "$que_03");
$args = array(
'post_type' => 'product',
'posts_per_page' => -1,
'product_tag' => $que_01
);
} else {
if(isset($_POST['cat'])) {
$tags = $_POST['cat'];
}
$args = array(
'post_type' => 'product',
'posts_per_page' => -1,
'product_category' => $tags
);
}
$loop = new WP_Query( $args );
$product_count = $loop->post_count;
if( $product_count > 0 ) :
while ( $loop->have_posts() ) : $loop->the_post();
global $post;
echo $thePostID = $loop->post->post_title;
}
endif;
?>