To dream that you have reincarnated into someone else, suggests that you have changed. You are not being yourself. Alternatively, it indicates that you are undergoing major changes in your life. If you reincarnated into an animal, consider the qualities of the specific animal.
Dreaming that you have died and reincarnated might represent a fresh start or new beginning somehow in your life. Depending on what kind of life you reincarnate into, you may be feeling good about the way you're leading your current life, or you may be feeling guilty about it, or otherwise.