Have you noticed that when you need to use the rest room, the closer you get to one, the more you need to!?

JUst wait kiddie-till YOU get to be this old. 

It has been known to happen.  See, you have a conditioned reflex, you have taught your excretory system to go when you get to the toilet; but sometimes it thinks you are at the toilet when you are only near it.  A little operant conditioning - such as waiting half a minute once you get to the toilet before you use it - would probably solve this problem.  Unless there is a physical reason for it of course.

Why do you say rest room when you mean toilet?  In answer to the actual question, the only time that happens to me is if I left it longer than I should have anyway.  When you need to go you NEED to go so do GO.