How do I animate a grid with opacity going from 0 to 20 but in random intervals

Hello, the title pretty much says it all. How can I animate a grid with the opacity to always fade from 0 to 20 and 0 again and do it in random intervals, like in this video (Visualization of a grid of blue circles fading in and out), cause I don't want to do it one by one, it takes too much time.​ Here is the grid that I want to use (I have it single layered and multiple layered, so no probs, just tell me the easiest way for you). I'm talking about animating the opacity on all the single triangles. Hope you can help and thanks in advance!