Existence is caused by a being that already exists?
How does that work?
I think God exists; He did not cause Himself to come into existence; He simply has always existed. And I find it to be a marvelous wonder how there is anything, at all, in existence . . . versus there being nothing. And I do experience God and His love.
If you are suggesting that God is merely the property of existence, I'll just suggest that this may run into philosophical problems.
I would say that God simply exists, and I might not concern myself with if His existence is a property or not; but it is a reality, in any case

. . . a fact, whether you call "it" a quality or property or not . . . whatever words you use. Oh . . . by "you", I don't mean you, Eudaemonist, but you people, in general . . . anybody
More accurately it would be "the existence of contingent things is caused (ultimately) by a being which not only exists, but IS existence." (IE a necessary being)
I think it is an interesting issue, if God has brought anything into existence. Did God bring things and conscious beings into existence, from "nothing"? Or did God "use" substances already self-existent, to make all He has created? You can create with what already exists. But such substances other than God would be inferior to the being of God.
In any case, Paul says God is the One "who gives life to all things", in 1 Timothy 6:13.
And the Bible says "God is light", in 1 John 1:5; and we see how sunlight gives life to natural beings on this earth . . . possibly as a natural representation of how God, really, is the One "who gives life to all things". And we see how, in the dark, ultraviolet light can in a way bring things to life, to be seen, experienced. Possibly, God then does not bring things into existence, but He has formed them and given them light to cause them to have conscious experience and be experienced.
But when light "hits" something, each thing responds according to its nature.
If we are in God's love, then, we benefit the most from His light. But if we are selfish and light comes, we can make a stink and suffer . . . because of our own nature. A healthy plant will grow in light, and in that same loving sunshine a plant with unhealthy roots will dry out and harden.
So, I consider that God may not actually bring things into existence, but into having conscious experience.