I did try - "if platform is not moving (also tried if 8 direction is not moving), wait 5 seconds, set animation to Bubble, wait 5 seconds, set animation to Sleep" but the animation would restart unpredictably during gameplay.
Having a random animation play after a certain amount of idle time seemed like a great idea but I'm not clear why this is not working. I set the timer low so I can see the result right away when I'm testing it. It was set to 300 and it still did not work.