Get the speed report of your website (like the screen shot below)  and suggestions on how to improve the speed of your website with GTmetrix. GTmetrix report can give you the full picture on how your website loads and it can help detect where bottlenecks are.



Some more ideas for optimizing your websites (mostly for your CMS websites like wordpress);

1). Disable plugins that consumes lots of server resources. According to https://onlinemediamasters.com/slow-wordpress-plugins, below are some plugins that may use up lots of server resources especially CPU;

    AdSense Click Fraud Monitoring
    Better WordPress Google XML Sitemaps
    Broken link checker
    Constant Contact for WordPress
    Contact Form 7
    Contextual Related Posts
    Digi Auto Links
    Disqus Comment System
    Divi builder
    Essential Grid
    Fuzzy SEO Booster
    Google XML Sitemaps
    Jetpack
    NextGEN Gallery
    NewStatPress
    Reveal IDs
    Revolution Slider
    S2 member
    SEO Auto Links & Related Posts
    Similar Posts
    Slimstat Analytics
    SumoMe
    VaultPress
    Visual Composer
    WooCommerce
    WordPress Facebook
    WordPress Related Posts
    WordPress Popular Posts
    WP Statistics
    WP-PostViews
    WP Power Stats
    wpCloaker
    WPML
    Yet Another Related Post Plugin
    Yuzo Related Posts

2). Ensure your CMS such as WordPress, all plugins and themes are updated to the latest version. NB: Please ensure you backup website files and database before commencing with this.

3). Prevent Spambot (Non-human visitors/spammers) with use of CAPTCHA on all forms on your website including the comment form.

4).  For mostly wordpress websites, use page caching to generate static HTML versions of your content. This can simply be achieved by installing  plugins such as WP Super Cache (recommended) or W3 Total Cache.

Please submit a support ticket if incase you need further help on improving the speed of your website mostly  wordpress website(s)/CMS.