Possible memory leak? blue screening on any game after random duration

My PC keeps bluescreening and saying it has ran out of memory even when it still has like 20gb ram spare. It also seems a bit random as to when it crashes but definitely gets worse over time and when stress is put on the pc. I assume its a memory leak of some kind but it seems to happen every time I play some kind of game and definitely isnt tied to one specific program. I dont really know what to do. Can anyone suggest a way to diagnose what might be causing this or a possible solution? when i google all i seem to find is take ram out of pc and put it back in again. hope someone can help me. Thanks