An extremely simple analogy of course, but ultimately this is why my money would be on an intelligent agent, it's the only phenomena which can crack that persistent paradox of self generation, infinite regression, etc. something which is ultimately natural in origin yet thoroughly unnatural in it's capacity to create what 'nature' alone never can... itself
Unless the universe started with something very simple and dumb, and has become more complex by evolution and iteration. In which case, God may be its goal, not the start point. This neatly accounts for why God doesn't exist yet.