Slow Linux Server Problems

I have several clients attached to different servers that are having a similar problem. When they are working in the office (with the Domino Server on the same physical network) performance is consistently good. However, when they are at another location (home, branch office etc.) A definite slowness occurs when the server has not been accessed for a period of time. Once a database is opened, for the most part, performance is similar to that experienced in the office, however, if the user works in another application and then returns to Notes after a few minutes, if can take 1-2 minutes to then get a response from the server. Once the server responds, all is well. I am getting complaints about this from different clients on different servers and I have experienced it myself. This only seems to be a problem with Linux servers - I don’t have a lot of clients using windows servers but I haven’t had any complaints from them. I have examined the logs and configurations at both the notes and linux level and can not find any error report or reason for the slowness. Any ideas how to troubleshoot or resolve this?