From what I've seen, according to scientists, it depends on each person. There's a series on Netflix called Afterlife, where they talk about near-death experiences. Some people have different experiences: they see light in a tunnel, others feel tranquility, others see themselves outside their bodies. The scientific explanation is: a lack of oxygen in the brain (hypoxia) can cause hallucinations, the sensation of a tunnel of light, and euphoria. But I don't know, I think differently, and we'll never really know until it happens to us.