I have a production web server that makes sites to be very slow when load for first time. After the first time all connections are normal and fast.

In the following screen you can see the first test I have run for a random site in my server:

and here you can see the result of the second time request:

As you can see there is a big change in the second load of the same page.

Here is the page load time graph:

My problem is that I don't really know anything about Red Had Linux server, and also I don't know where can I start.

Can somebody to help me ? I like to find out the solution for the long time "wait" in connection.

I know that my question is very minimal, but you can always ask me to give you information about the server.