Browser is “Connecting” to site on each page chang

Question

In Chrome dev tools, on Network tab, loading HTML page of normal website (e.g. StackOverflow) at first time looks like this:

... if I continue browsing this website, the "Connecting" time is not present anymore, and request to HTML file looks like this:

But on a website that I'm working on, the "Connecting" time is present on each page load:

In Chrome dev tools documentation "Connecting" status is explained as: "Time it took to establish a connection, including TCP handshakes/retries, DNS lookup, and time connecting to a proxy or negotiating a secure-socket layer (SSL)."

I'm using apache and sending request to simple static file. Do you know what can cause this and what might be wrong in config of server?