According to the Doctrine of the Trinity, is God split up?

As the question goes: is God split up? I have this theory, and hopefully, I'm not alone in this, that God the Father was one, before He split Himself into three, meaning that the trinity must be wrong and that God is one, Jesus is one, and that The holy spirit is one, but, that God was one, before the beginning, and that He split Himself into Jesus and The holy spirit as well. I am myself thinking that this is true, but I'm also afraid I may be wrong. Anyways, I'm looking into it! And I would be glad if anyone could point out to me for instance church fathers or others with the same mind set.