Seems there's quite a bit about "before" life it just doesn't get discussed as much because the mainstream/dominant traditions in modern Western English-speaking culture are death-preparing traditions (aka, they focus on "after" life).
I mean, as far as I'm aware Christian traditions basically teach their god creates the soul, and that soul is created at conception. This is why some of them argue that "life" begins at conception in the first place - it's a religious argument at its core. Dunno if others Abrahamic traditions differ, or whether there are big differences amongst the different Christian traditions on this issue.
Then there are many other traditions that widely acknowledge that souls go through many cycles of incarnation and are recycled like pretty much everything else in the universe is. As far as I'm aware, that's how karma proper works, as opposed to the Westernized version of it - karma is what comes from past incarnations, not the present one (which will influence the next incarnation).
And then there are philosophies that understand the very notion of "self" or "ego" is a non-starter since there is no "I" without "thou" - existence simply is and pointing at a "before" or an "after" are equally nonsensical. It is an understanding that ego-centered conceptions of time and space are not the reality of things and a letting go of that.
All of these various tales are interesting, in their own way. I add to it what some would consider a naturalistic approach, told best by the Universe Story that acknowledges that every atom in our very being was here at the beginning of the universe (if it had a beginning) and that we were all there, at that moment, and will be there when the universe ends (if it ends).
My beliefs fall in this mix. Even as a young child being schooled in protestant Christianity, long before I knew anything about the eastern traditions, even before I learned anything about science, I believed in reincarnation. And not the coming back a horse kind.
Thoughts to ponder just from the Bible:
Ec 1:9-11 "9)What has been is what will be, and what has been done is what will be done,and there is nothing new under the sun. 10) Is there a thing of which it is said, “See, this is new”? It has been already in the ages before us.11) There is no remembrance of former things,
nor will there be any remembrance
of later things yet to be among those who come after."
Ec 12:7 "and the dust returns to the earth as it was, and the spirit returns to God who gave it."
Ec 11:5 "As you do not know how the spirit comes to the bones in the womb of a woman with child, so you do not know the work of God who makes everything."
Je 1:5a "Before I formed you in the womb I knew you, and before you were born I consecrated you;"
Mt 11:14 [Jesus speaking] "and if you are willing to accept it, he is Elijah who is to come."
He 7: 1-3 "For this Melchizedek, Kong of Salem, priest of the Most High God,....is first by translation of his name, king of righteousness, and then he is also.....king of peace. He is without father or mother or genealogy, and has neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever."
He 7:15-17 [speaking of Jesus]
"15) This becomes even more evident when another priest arises in the likeness of Melchizedek, 16) who has become a priest, not on the basis of a legal requirement concerning bodily descent, but by the power of an indestructible life. 17) For it is witnessed of him,
“You are a priest forever,
after the order of Melchizedek.”'
