Set the entire movie to a very fast frame rate. Have a variable called "delay" and "currentFrame" associated with the movie clip. Then randomly set the value of delay. Then do an if statement to handle the movement inside of the onFrameEvent(enterFrame):

Code:
if (delay == currentFrame) {
     moveClip()
     currentFrame = 1
} else {
     currentFrame++
}
You could easily create an array on the main timeline that contained all the movie clip names and then have a controller clip that loops over the array and does this every frame. This should work just fine and its pretty simple to implement.

Mike Grundvig