Random ingame crashes.

My game randomly freezes for no reason at all, and that for about 6 or maybe even more months. I have to open the task manager and my game has "no response", so Im forced to close it and start reconnecting. I already tried reinstalling and using the hextech repair tool, but it didnt help. I play with borderless and not fullscreen and the freezes occur at random. For a while it only happened in aram and sometimes it doesnt freeze for days but now it starts freezing in Summoners Rift again. I also didnt see a fix to this problem on another thread.