It is, and that’s inherent in the problem under consideration, the problem of the ‘uncaused caused’ or the ‘first mover’. Logic can either be A) circular or B) not-circular. Any not-circular logic must explain each element by referring to a prior, but then you’ve got an infinite regress. So you’re trapped in a dilemma: do you want the circular logic or the infinite regress? Liebniz’s choice was to say that God was inherently existent, like when Lao Tzu said 道法 自然
There’s no reason for a necessary being to exist before it does
Correct. It is necessary: it is self-causing. It does not stand upon a ‘reason’, unlike everything else in conditioned existence.
to exist before it does
You’re assuming it is subject to the laws of linear time and causation, and point out how that assumption leads to a contradiction. But Liebniz’s God is not subject to the laws of linear time and causation. Which is the whole point of positing it: because if it were subject to those laws: infinite regress.
and no evidence that one does in the real world.
Well the world exists, so all this existence must have some cause. That was the starting point of the conversation: Why is there something instead of nothing?