1. You have a many Nameservers. ie: more then 4 or 8 to 10 name server.
2. DNS not configured properly
3. Overloaded server
4. Slow DDoS/DoS attack on your site.
If you are using wordpress then also make sure that wp-login.php and xmlrpc.php is protected by .htaccess and only accessible by your selected/whitelisted IPs.
Your website's slow loading time could be due to various factors such as large image files, excessive use of plugins, inefficient code, or insufficient server resources. To improve the load time, consider optimizing images, minimizing HTTP requests, leveraging browser caching, and upgrading your hosting plan if needed. Monitoring and resolving these issues can significantly enhance your website's performance.