Most would agree that God's nature is eternal and unchanging. Did God choose his nature or is it determined by some factor outside himself?
Your question could unleash years of philosophical debate.
To be able to even discuss it without talking past each other requires defining the terms used.
Without defining these words, nothing can happen but wheels spinning in the linguistic mud:
"God".
"Nature".
"Eternity".
These cannot be defined without first defining the words that would have to be used to define those things:
"Is",
and
"Exist".
This will lead immediately into a tautology: existence can only be defined in terms of itself.
That which is, exists, that which exists, is.
It is unsurprising, then, that the forms of the verb "to be" are intricately bound up in the concept and name of God.
Of course, to avoid the tautology, one has to find some other reference point. Trouble is, with "existence" and "being", there isn't any other reference point, by definition, unless one wants to consider the notion of nonexistence and emptiness to be the opposite of existence.
Does nonexistence exist?
Is nothing a thing or just a word?
Is empty space a thing, or the utter lack of a thing.
If one defines existence as including nothing, and nonexistence as being part of existence if only as a concept, one is rounding the corner to begin the first discussion of the definitions of the necessary words to have the conversation you propose to have.
I propose the following definitions:
(1) Existence and being. To exist is to be, to be is to exist. That which exists, is. That which is, exists.
(1)(A) Thoughts exist, though they may not be material. (They may be, if thought is purely a chemical structure. But if there is a detachable spirit, such as Near-Death Experiences and all Jewish, Christian, Hebrew, Hindu, Buddhist, Jain and pagan religion holds, then thoughts can and do exist without any material. In any case, whether material or not, the fact that we are experiencing thoughts right now reading and writing this demonstrates empirically that thoughts exist as SOMETHING, and as such are part of "existence". They "are".
(1)(B) Nothingness may not exist as a material thing. (The actual space between stars, "outer space" is not really a vacuum. It is a very rarefied plasma of transiting light particles (a photographic film exposed to outer space will wash out with light in time, so "outer space" is really a sea of particles).) To find true vacuum one could go within the crystal latticework in a rock deep in the bowels of the earth, where there is neither air nor water, nor ambient light particles nor anything else but the occasional odd neutrino passing through. This would be (or could be) "true" vacuum - dead space between atomic particles that is literally composed of nothing. That "nothing" is itself certainly a thing, because thoughts are a thing, but it is a thing without material existence. It's only property is that of dimension. (Then again, within each cubic Planck-length space within there COULD be a quantum foam in which existence and non-existence fizzes and pops - or that whole concept could itself be nothing but an imaginative mental contruct, which does not exist in tangible reality, but which does exist as a matter of thought, like Romulans and Vulcans.)
(2) Given those definitions of "Existence" "To Be" and "Nothingness", we can then proceed to define "Nature" precisely for our purpose. Nature is the behavior of that which exists materially (including empty space). That part of the definition is fixed. Nature may or may not include that which is purely thought and mental construct.
In this way, we can speak of a set of things as Nature, and then speak of the apparent laws that govern it, and we leave open the possibility of a larger set of things that are also nature, that include the world of thought.
This problem of thought will emerge throughout our discussion (if we ever go on to have it), for the dichotomy between the physical and the mental, the material and the spiritual, is THE issue that we are grappling with. We live in a universe with concrete points that we can see and touch, using a mind that obviously works, but whose existence is (perhaps) a non-material mystery. And given the self-evident existence of mind, the question of God is the question of whether or not there is an overmind, a spirit that does not live in the physical or require it. Is our thought and mind the intrusion into the reality we can perceive physically of an aspect of existence that we cannot see other than in this way (or through revelation by another mind somewhere)? Or is our mind nothing but the physical/chemical phenomenon generated by a deterministic meat machine?
Definitions at least help us grapple with what we're talking about, which is, at root, God.
(3) God is certainly that which is omnipotent, omnipresent and timeless (or eternal). That God could be an "It": Natural law - the law that governs that "Nature" we have defined (if there is a natural law). But if that God has a mind and is also omniscient, then things get much more interesting. And given that WE have minds, obviously, the universe - which is to say the manifestation of nature - at least perceives itself in a certain way, through us.
Is there a mind over ours? And if there is, is there a mind over that one? Is there ultimately a mind behind natural law that makes it be? If so, that is a theistic God, and is the God of the Jews, the Muslims and the Christians, and "It" becomes a person - a "He" (or possibly "She"). If not, then God is simply the unthinking laws of nature and pantheistic. In any case, given our definition of God, God exists in some form by definition, because Nature is, and behaves regularly, and has a law that makes it do so. So, the really interesting question is whether God has a mind or not - that determines whether God, which is that which is (or the cause of it being so), is pantheistic or theistic.
We can assume a theistic God by definition and move on, or we can pause and demonstrate, from the evidence we have available to us, that it is more likely than not that God is theistic.
(4) "Eternal" would be defined as "that which always was, is, and always will be", or it could be alternatively defined as timeless (which is more nebulous). To really define it, we would have to define the concept of "time".
Note: I'm really trying to wrestle with the essence of things here, so that a conversation can be had using a common, agreed upon lexicon.
If in the end it all looks like mental masturbation, then maybe this discussion isn't for you.
With those terms defined thus, I can answer the question you posed.
But it will take some space and isn't worth doing if you're not interested in seeing the answer.
So, it's up to you.
Do you accept these definitions of terms, or would you like to adjust some of them?
Shall we go on?