UNIVERSE OUT OF NOTHING

Could Universe create itself out of nothing?

I had read that another physicist once asked Einstein that
since total negative gravitational field energy of a star is equal to total positive energy of mass of the star,
isn't that mean total energy of the star is zero?
Isn't that mean a star could come to existence out of nothing (since apparently no energy is required)?
Isn't that also imply maybe the whole Universe could come into existence out of nothing?

Quantum Mechanics already tells us that all kinds of particles, called virtual particles,
come in and out of existence everywhere in the Universe(?) all the time (due to Quantum Uncertainty).
The reason they called "virtual" particles is because they cannot be detected directly.
And the reason for that is because they stay in existence for a very short time, not nearly enough to detect them.

Now the question is why we never see stars or anything else in the Universe come in or out of existence?
What we see instead is mass and gravitational field of all stars always stay separate.
Even when a star collapsed to a Black Hole, central positive mass/energy and its negative gravitational field energy around,
never destroy each other.
And while virtual particles come in and out of existence, real particles always stay in existence,
just like stars, just like Universe itself.

Then why virtual particles must go back out of existence so fast, after they come in each time?
It must be due to their mass/energy being borrowed from the vacuum (space-time or some other Universal energy field?).
If so, isn't that imply mass/energy of real particles is not borrowed?
And isn't that also imply mass/energy of Universe is not borrowed?
If not borrowed then what that means?
Isn't it mean, there is no way for (any) Universe to create itself out of nothing and stay in existence?