Vanakkam,
This is very interesting question, I have been wondering the same thing but...Not on the same side !
I don't know exactly "when" a soul enter a body, I don't remember much thing from any past time
But the relationship and the feelings a mother have, like Vinayakaji described, when she is pregnant is sure a sign. The sound of water, some posture, also have impact on childrens and adults as they consciously or inconsciously remind the womb....So there must be some kind of consicousness in here =0 Like Sri Vishnuji sleeping, in the state where He dream the next world, maybe we are like that in the womb, dreaming our next life ?
I was wondering about when you die ! There have been very much testimonies from people that experienced death, or near death experiences. Those people are from all around the world, events scientifically witnessed, so I personnaly give credits to their sayings. But this confuse me regarding reincarnation ! Since almost all of that people said they were feeling bliss, light, and saw dead relatives/animals dear to them !
I though at the time of death only the Atman remain, which is not our appearance/personality/ego. And at the time of next life, only the atman enter a new body and make new life, ego, physical features....
...But why do these people saw dead relatives while experiencing death/near death ? I mean, they shouldn't have their ex-physical appearance, or even be there as they should be merged with Brahman or in another body
Reincarnation is not very much discussed, I don't really know why, as it is a very interesting topic that can help understanding more how everything works
Aum Namah Shivaya