Site running incredibly slow

An old site we host is running incredibly slow (version I've checked the server Space, CPU and various limits and all seem to be well. It might be a cron job-related error. Any advice gratefully received.

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lukasznillo replied on at Permalink Reply
Hey. You have a large number of scripts loaded from different domains. Everything can be seen in the browser console. E.g - block render for 21 s. So in my opinion the problem is in website optimization and its first to check.
JohntheFish replied on at Permalink Reply
Also look carefully at your autonav settings. An autonav grabbing more pages than actually needed is a frequent cause of slow response.

(Edit: sorry, speed analyzer is not relevant for a 5.6 site)
For investigating speed within a site, install the free Speed Analyzer addon