Godexists .... I agree that a vacuum is not 'absolute nothing'. It still exists within the framework of spacetime and is subject to fluctuations happening at a quantum level.
However, I disagree with your assessment about virtual particles being caused by the vacuum.
We know that in between elementary particles (i.e. quarks) there is empty space (vaccuum). We know the vacuum fluctuates. This does not mean that the vacuum itself causes the fluctuations. That's circular. It just fluctuates with no apparent cause.
These fluctuations are fields of basic force interactions. They can be electric or magnetic force fields. These fields are called 'virtual particles'.
So the vacuum fluctuates and these fluctuations manifest as various types of force fields (virtual particles). They come into existence and, as they encounter each other in opposing forces, they annihilate each other out of existence.
This happens... but without any apparent cause and also completely randomly.
Although this happens within the framework of spacetime, it is not spacetime itself that is causing the fluctuations either.Radioactive decayWiki
is a better, more clear example of how something can happen without a cause, completely spontaneously.
About the universe coming from nothing, we don't know. It may very well be that the framework required for the universe's beginning to happen has always existed. But science has yet to define or even detect what, if anything, that framework may be.
Given your username, I suppose you are going to posit that a 'god' exists and it created the universe?