Be sure to manually remove the entire contents of the cache folder and do the following steps:
a) enable separate CSS
b) exclude unnecessary post types: a
Afterwards rebuild the cache and see if the problem is solved.
This usually happens if there are a very large number of pages or if there is a dynamic part in JS or CSS – some themes/plugins creates dynamic js and that is why the folder is filled up.
Be sure to manually remove the entire contents of the cache folder and do the following steps:
a) enable separate CSS (styles) and separate JS (Scripts) in Optimization settings:
Settings > Optimization > Scripts: Separate Scripts
Settings > Optimization > Styles: Separate Styles
b) exclude unnecessary post types: autoconfig should find most and exclude them automatically but you can add them manually: Settings > Caching > Exceptions> Exclude Post Types