The most common reasons your Wordpress site is slow to load are:

1. Slow or poor quality hosting that doesn't match your level or traffic or site
2. No caching or caching plugins in place
3. You have a high traffic site but no content delivery network (CDN) to reduce the load on the hosting
4. No image compression or HUGE pages
5. You’re not using HTTPS or taking advantage of the HTTP2 protocol
6. The version of PHP you’re using is old or out of date
7. You have slow or out of date plugins.

To fix it: 

1- Use high quality website hosting (i.e. get rid of your bargain basement hosting)

2- Use caching (a must-do for Wordpress)

3- Use Cloudflare and/or a Content Delivery Network (CDN)

4- Compress & Optimize Your Images

5- Switch to HTTPS (versus HTTP) to take advantage of HTTP2 Protocol

6- Disable any plugins you’re not using

Thank you for your help