FPS drops in 2nd half/in menus

Every single time I play this game I have the same problem. I play a match during the opening cutscene I have stuttering. First half its okay 60 fps constant no drops no nothing. But then from the 2nd half My FPS drops to 5-10 and its to the point where I have to restart and get DNF's only for it to happen again and again sometimes even after I open packs it becomes laggy in the menus!