Extremely bad server response times and page load times

I am getting outrageously bad server response times and page load times on a digital ocean WordPress image installation. I have used this many times in the past without any issue. My load times are between 5 seconds to 60 seconds averaging around 10 seconds. Similar setups I’ve been getting <2 seconds in almost all cases. The first packet/first byte often shows >3 seconds.

There is absolutely nothing to explain this.

Server load is 0.00 - 0.10 There is plenty of free memory There is plenty of free swap file space CPU is mostly idle There are no errors or warnings in the mysql error or the apache error log There is nothing abnormal in the apache access log

What can possibly be causing such terrible performance?

Waterfall tests show that most resources are loaded with pretty poor times but 2 or 3 static resources like images or javascript files take 5 seconds, 10 seconds or even more to load. (maybe 50kb or 100kb per file).

How can I diagnose the problem?

Thanks.