Not random, but for bulk transitions.
I don't think this is what you want, but it's the nearest thing to it I can think of.
You will now have those three transitions repeated through the project in that order.
Insanity is hereditary, you get it from your children
In versions 9 and 10, you can also select an entire sequence, right-click and select Apply Default Transition. (You can also set any transition to be the Default Transition by right-clicking on it in the Transitions panel.)