computer keeps freezing

so this has been going on for about two weeks ill turn my computer on and get onto league and after the champ select happens the game goes to the loading screen for match and it freezes my entire computer and i cant even task manage when it does i have to reboot the thing and this last time it did it my computer rebooted automatically but it always happens in the loading screen and my drivers are up to date it doesn't freeze doing anything else except league if anyone has any suggestions please help...