Lazy loading

Slowness/high CPU usage could be due to (but not limited to):
– A poor or memory intensive theme. Switch to the WordPress default theme and test loading time and see if you see a difference. If you do, may be your theme can be re-written to be more efficient.
– Poor or memory intensive plugins. One by one disable plugins and test loading time and see if you see a difference. If you do, may be that plugin can be re-written to be more efficient.
– your server is slow (e.g., “process hang”, overload, you get a lot of visitors, other problems, etc.); generally, every inexpensive host out there is slow.
– I don’t know if you use CloudFlare or not but if you do I would suggest deactivating it and seeing if it helps. Also sometimes a good purge of the cache on CloudFlare can help.
– Lots of images can cause slowness. Also images loaded without compression.
– Lots of external content (facebook/ gravatar/ google adds, etc.) and redirects in general tends to slow sites down.

The pingdom, etc., report tells you exactly what is wrong with your site: https://tools.pingdom.com/
https://gtmetrix.com/leverage-browser-caching.html ; https://developers.google.com/speed/pagespeed/insights/

Use plugins to optmize/speed up sites: Autoptimize, WP Super Cache , etc

Use Jetpack’s Photon option to speed up image delivery ; Also see this tutorial: http://www.wpbeginner.com/beginners-guide/speed-wordpress-save-images-optimized-web/

ueful codex: – http://codex.wordpress.org/WordPress_Optimization