The delay trick works, but that means your first run is the same, you can put a delay in front, but then you have dead time initially. Just depends on the affect you want.
But if neither of those cut it this is what i did
random value (between 0 and 30 in my case cause my time line is 30 seconds) and then using a sequence before it in order to fire the new time value.
I wrestled with this for awhile before i realized you had to fire that Set New Time pin in order to get that random value to do its thing
the do once just stops it from unessarly firing over and over, though in hind sight it should only fire once anyways. But if you were firing this off tick then the do once would be usefull