wp_update_post question on array

wp_update_post expects ‘ID’ to be a single post ID, not an array. You will need to handle each post separately.

Try:

$post_ids = array( 1235, 1234, 1228, 1221, 1211, 1212, 1208, 1200 );

foreach($post_ids as $post_id) {
     $post = array( 'ID' => $post_id, 'post_status' => 'pending' );
     wp_update_post($post);
}