Caching Problems

Hi all – I would appreciate some advice about caching plugins. I’m using WP Super Cache now but this question is not specific to this plugin.
When manually testing my site speed if I randomly click between any 2 pages or posts the response time is slow (3.5 seconds). Having done that if I do it again the response time is very quick < 1 second. I am presuming thats because those 2 pages are now cached.

Google Analytics show my page lad time as 3.2 seconds. This must be harming my SEO.

If thats the case surely it would be logical for the caching plugin to ‘preload’ all pages and posts automatically so visitors to my site are automatically served cached results and the site. Maybe refreshed on a daily basis? Are there any caching plugins that do this.

My thanks