Hidden Content can be briefly seen when Page loads

I am using collapse-o-matic on the following page. When the page first loads up, the information which is supposed to be hidden can be briefly seen before it disappears.

https://www.wonderofherbs.com/how-to-read-and-interpret-scientific-studies/

How do I prevent this happening? I have been trying a few text hiding plugins and this is the only one that has this issue.

https://wordpress.org/plugins/jquery-collapse-o-matic/