Every human imo has three sides. Emotional, rational and spiritual. The most rational explanation is the theory of evolution. It beats believing in an invisible being you cannot see or hear or feel. The first and third are more spiritual than rational. Agnosticism is more emotional, you crave a connection with a higher power but at the same time think its ridiculous.
@Nanubot, if you are bothering to care what the God of the Bible says, then you've already bought into a religion. Christianity is a religion. The reason your God never told you to accept a religion is because you have to accept a religion as a prerequisite to care what he says at all.
The Bible itself isn't a religion. It's a book. You can believe in the Bible, but not submit to Christianity or being Catholic. I know some people who 'believe in the Bible' exclusively, rather than being Christian. You don't need to be Catholic or Christian to realize that God is real and you believe in him.
I don't see Agnostic Atheism here. Prefix a is basically a negation. Gnostic refers to knowledge: I have no certain knowledge that no gods exist. Theism refers to belief in god/s, I do not have a belief in Gods.