"Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters." Genesis 1.2
Plato initiated the "cosmological argument" for the existence of God by pointing out that everything depends on something and therefore something or someone must ultimately be responsible for kick-starting life. Aristotle extended the idea through developing the concept of the "Unmoved Mover". And, on the classical understanding that all created things and creatures must derive from a Creator who possesses all of their qualities to a superior degree, rather than being conceived of as an anonymous "force" this Unmoved Mover is more appropriately thought of as the One we call God.
It's a neat idea but more recent scientific and philosophical insights, from Isaac Newton onwards, have suggested a more complex causal chain, involving biological evolution and quantum physics. Does that do away with the need for a "Prime Mover"? Not necessarily but, for proof of God's existence, we need more than the Cosmological Argument on its own...