Crashing during game play

Anyone know whats up with this? for the last 2/3 day's ive been getting a crash, I'd crash in game with the PC giving me a notification sound ( ding ) with no error msg. When i open task manger i can see the client isnt responding, therefore i have to end task and reopen game. I've scanned my pc many times reinstalled league about 4 times, I have tried SR and i dont seem to be getting this problem, It only seems to be in TFT.