Your issue appears to be in the cache based on the comments.
When an automation suite kicks off it will typically clear all of the cache and treat it like the very first time that browser has ever been run. This will cause any scripts or images that are large and have longer loading times to be re-downloaded/processed/whatever.
This is really good for automation because it leads to clean, fresh runs that don't have stored data that corrupt the run. The problem though is that it will slow down the application drastically.
There are ways to disable this piece within most automation tools, though I would personally recommend against doing this unless you specifically wanted the test(s) to contain cached data.
Ultimately, I would recommend reaching out to the parties responsible for this and see if the uncached load times are acceptable. If not, file a defect.