Why do i keep getting disconnected from xbox live?

Whenever i turn my xbox on, it is supposed to sign me into xbox live automatically. It says i am not signed in and takes me four trys to get it to finally work. I keep losing connection to xbox live partys. I dont know how to check or change my NAT settings. My internet is not the problem, it is running fine. I have the router that attaches to the back of the xbox that is made by microsoft. Someone please help me!