Where did all the matter and energy in the Universe come from originally?
Nothing.
Previous universe. Or God.
There is a phenomena in quantum mechanics known as virtual particles. A particle/anti-particle pair spontaneously erupts into existence, than anihilate each other before the rest of the universe even knew they existed.
Perhaps the same thing happened to our entire universe.
Our universe and an anti universe may have been spontaneously created in a greater Omniverse.
The usual way that physicists deal with this question is… to not deal with it. You’ve got to know your limits, and apparently, “before the Big Bang” (whatever that means) is beyond the limits of physics. You wanna say it was God? Physics has no problem with that. You wanna say it was the toejam of the Great Cosmic Aardvark? No problem with that, either. Ignore the question entirely? That’s OK, too.
This isn’t something Mr science can answer yet…we’ll have to consult Mr science’s father for this…Mr philosophy =P