I believe consciousness is on a spectrum of self-awareness. It just exists, perhaps even without evolutionary need. Even if you act mainly on instinct or even purely you could still very well be conscious.

You will continue to exist as long as conscious life is able to propagate. For me, it makes sense that a state of nonexistence can't exist. Your consciousness is not unique, it's only a physical phenomena, thus it can be replicated, and it doesn't even have to be exact, after all, you are the ship of Theseus. When you make a clone and kill the original, the clone is the original, exactly. Like waking up from a dream, to suddenly being teleported somewhere. When you go to sleep, why don't you wake up as a rabbit? Who says you don't? Consciousness so far can only be examined from the outside but this does not deny our subjective conscious experience. I believe that when you die you will just move on, not as the same person, but as another conscious being. Eternal life. Essentially immortal, but you lose everything, and you're unaware of it. Even if 5 million years have to pass, you will just wake suddenly wake up.

I also believe consciousness is not quantifiable, but shared, and you just have a narrow perspective at a time. When you die I'd say you don't even have to wake up as a newborn, you could just spontaneously be another person, as long as there's no other path of continuity.