Apply the following expression to a Scale property to make a layer wobble at each marker:

  n = 0; 
  t = 0; 
  if (marker.numKeys > 0){ 
      n = marker.nearestKey(time).index; 
      if (marker.key(n).time > time) n--; 
  } 
  if (n > 0) t = time - marker.key(n).time; 
    
  amp = 15; 
  freq = 5; 
  decay = 3.0; 
    
  angle = freq * 2 * Math.PI * t; 
  scaleFact = (100 + amp * Math.sin(angle) / Math.exp(decay * t)) / 100; 
  [value[0] * scaleFact, value[1] / scaleFact];