Champion stops responding

For almost three months now I've had this issue where during a game my champion will randomly stop responsing. Everything else around me moves normally but my champion just sits there and will not respond to clicks and I can't cast anything. This happens for a random amount of time, usually several seconds. On some occasions animations will stop (as if there was a massive lag spike). I have tried reinstalling league and it hasn't fixed. It gets to the point where I actually can't play.