I have a server that's hosted in a colocation facility. Recently the websites it hosts have been running slowly. Sometimes a page will load immediately (like it used to always) and other times it just won't load at all, and the request will time out. Clicking the link again usually gets the page to load, almost immediately.
Nothing's changed on the server since it was installed a few years ago, so I'm having trouble working out what the problem may be.
When I ping it, it seems normal. Also, the traffic volume is not particularly high. It has plenty of free disk space. Connections over SSH seem to be fine. I've tested on different computers and different browsers, and at different sites (to eliminate my internet connection and ISP) and it's still the same issues.
How do I work out what the problem is? Any help appreciated.