open your Task Manager and see which process is using a lot of cycles?

Since this seems to, according to what you have said, only be happening when you first start up the computer it could easily be one of your start-up apps or services that hasn't finished that is interfering or it could even be a malware service attempting connection that interferes with your winsock.

Also take a look at your Event Viewer and the system and application logs to see if any problems are being logged.