HELP WITH GETTING THE DESIRED EFFECT (RMXP)

I'm making a cave where I want random shaking of the screen going on in the background. I made a parallel event using variables (random number) to have different degrees of shakes, then a short break and then have it go all over again. I put in a loop command but it only happens once.

It's supposed to seem like small earthquakes going on all the time you're in there.

Thanks for the info. I didn't know that.