Here's a thread where we discussed some similar(?) problems a year or so ago. As far as I can tell, there seemed to be two separate (but similar-acting) issues:

-- Predictable delays in the middle of the night (Eastern time) when I'd expect the server to be busy catching up on reindexing and other housekeeping tasks, and

-- unpredictable delays at other times, possibly associated with a failing hard drive. They stopped after the hard drive actually quit and got replaced.

I've been seeing few or no delays at PC myself in recent months. Last week, though, I was away from home using a paid computer with a satellite connection. The satellite signal turned out to be vulnerable to weather and other disturbances so the connection would sometimes slow to a crawl or go down altogether for a few minutes. That problem seemed to affect all sites but I was noticing it most on Psych Central because that was where I was spending the most online time.

What I usually do with slowdowns and similar problems is just observe and note what's happening until either I notice a pattern to the problem or it stops happening.