Ah, I see.
I don't think it is. The example you mentioned was reincarnation which is mostly a Buddhist belief and Buddhism doesn't have a personal God to worship.
Plus, agnostic atheism just means not believing in a God and not knowing if it can be proved or disproved (hence the agnostic part). I know some agnostics and atheists who believe in reincarnation or a possible afterlife.
So yes, it is entirely possible to believe in it without a supernatural being involved.