How come my Xbox 360 is starting to be slow and freeze?

It freezes during a game sometimes, and then i wait for about 5 minutes, and then it un freezes. If im in a party, it aalways says the party leader left and everyone else left, but after about 3 minutes everybody is in. The leader doesnt leave at all, i dont know why it does that. and when they leave it says joining or connecting to xbox live party. It wont let me connect to an xbox live parties (most of the time) at all. When i go to my friends list, my friends gamer picture and there status doesnt show.