Server blocking me for no reason?

When I wanna connect to any server, it takes a very long time until I am in it. (after I logged in). Then, when I close CF and start it again, and when I wanna login again, it tells me that I'm blocked from the server for 3-5 minutes. It ALWAYS happens to me. Could anyone help me with that? But when I waited that 3-5 minutes, I can login without any problems. But everytime when I start my pc and wanna play CF, this happens.