Yes, actually. It happens all the time on the quantum level. I suggest you watch Dr. Lawrence Krauss' A Universe From Nothing.
However, your argument defeats itself because I suppose somehow your "god" didn't need a cause, right?
you have observed thing on a quantum level ?

my, what an expensive labratory set up you must have..

hypothetically speaking, lets say you acually did observe a vitual particle pop into existence. the cause of that was a "wuantum fluctuation" .. and what was the cause of that quantum fluctuation ?? we dont know, and if we find out, we still have to ask , what was the cause of that cause ?

moreover, the idea that something can happen without an observable cause is teological in of itself. why did ancient man believe in God? because there was all this phenomena, all this life, and absolutely no cause to be found

must have been done by somebody

however , all that is just to address where you mind is currently at, first of all you have never observed something happening without cause. everything visible to your eye is completely bound to the laws of causality. its only in the real of theoretical physics that its hypotheisized that that law can break down. being that neither you or I or anyone else for that matter has ever observed anything happen without a significant cause behidn it, it is completely empirical to assume that the universe has a cause as well. and there is only one possible cause
