I am afraid I think the question What is the nature of God is meaningless unless you are a pantheist.
Nature is Phusis which is one of the roots of Being.
So the question can be transformed into “What is the Is (phusis) of God.”
If like Spinoza you think God is nature then it is merely a tautology. It boils in that case down to a question of the nature of nature.
It is unlikely that nature has any nature beyond nature itself. In other words, nature is a term that does not ramify and is thus unstriated.
Nature is more or less just existence and existence does not ramify.
On the other hand if you believe that God is not nature, then to ask the nature of god is a meaningless question, instead we should as the characteristics or essence of God, rather than questioning Gods nature.
God creates nature, and so God cannot have a nature himself.
I just cannot figure out what the nature of God could be in God creates nature.
If God is an absolute, i.e. is without ultimately characteristics, of the kind that things have, then there is no basis for God to have a nature beyond Nature.