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<?php
// This snippet: https://gist.github.com/cliffordp/c5fc837ba07a8037d040
// Adapted from https://wp-types.com/forums/topic/how-to-set-post-title-upon-initial-post-creation/#post-307205
// Another implementation to take into consideration: https://github.com/moderntribe/tribe-common/blob/4.12.12/src/Tribe/Tracker.php#L292

add_action( 'post_updated', 'my_post_updated_func' );

function my_post_updated_func( $post_id ) {
  // Only do for this post type. Change for your CPT
  $post_type = 'my-cpt';
  
  // Types custom field (gets prefixed with "wpcf-") that's used to set post title and slug
  $field_slug = "my-field";
  
  // If this is just a revision, don't
  if ( wp_is_post_revision( $post_id ) || get_post_type( $post_id ) != $post_type ) {
    return;
  }
  
  remove_action( 'post_updated', 'my_post_updated_func' );
  
  $title_and_slug = get_post_meta( $post_id, "wpcf-$field_slug", true );
  
  if ( isset ( $_POST['wpcf'][$field_slug] ) && ! empty ( $_POST['wpcf'][$field_slug] ) ) {
    $title_and_slug = $_POST['wpcf'][$field_slug];
  }
  
  $my_args = array(
    'ID'          => $post_id,
    'post_title'  => $title_and_slug,
    'post_name'   => sanitize_title( $title_and_slug ),
  );
  
  // update the post, which calls save_post again
  $res = wp_update_post( $my_args, true );
  
  add_action( 'post_updated', 'my_post_updated_func' );
}