Piwik very slow tracking response (25+ seconds!) (1 reply)

I have started seeing this behaviour where it takes 20-30 seconds for piwik to return the tracking request. See attached screenshot.

Here is what I have found so far:

It happens only on initial pageload if the page has not been accessed for some time.
If you wait it out (20-30 seconds) and then reload the page, the response on the second pageload is instant.

There are no slow queries
I checked the mysql slow query log, nothing is output. (I put 5 seconds as the slow query threshold).

Has anyone seen something like this? How do you fix it??

Thanks.