It depends on your server load, especially if you are on a shared server. It happens to all websites not just Oxwall. I have had it happen to very simple html 3 page sites. Although there are factors with any scripts this size that contribute to delays, it is primarily a server load issue.
Yes there are ways to check the average server load time as well as check to see what other websites are on the same server as you. It is pretty much public info. So if you want to know if your sites next door neighbor on the server is a porn site or other type of site, the informaton is out there.
If your server load time or uptime of the server is not good you can kindly (kindly is the key) ask you host about moving to another server. Depending on the host they will or wont, they are not obligated to do so.