I have been having speed issues for a long time and this last month it's worse than ever. Never consistent but between 25 seconds and 90 seconds. Terrible! I finally found the culprit and it was the plugin Wordfence Security. Disabled it and have now deleted that plugin, added the optimizing plugins that always promise to improve speed, now I'm loading at 2.9 seconds desktop to 12 seconds for mobile.
I hope you are well. Too much installation of unncessary plugin may cause website speed issues. Some plugins taking too much time for loading. It also put bad effect on user experience. Website should be responsive, user friendly and high loading speed.
Here's some methods to increase WP website speed:
Choose a better web hosting provider, For example Godaddy,