Few ideas from the psychedelic world capture the imagination quite like this one: that your body might produce a psychedelic all by itself. It sounds like science fiction, and in part it is. Time to separate fact from speculation carefully. This is an educational piece.
Is DMT really present in the body?
In very small, trace amounts, DMT has indeed been detected in mammalian body tissue, and research into this is still ongoing. That is as far as the factual part goes: there are indications that the molecule occurs naturally. What exactly it does there is an open question.
The pineal gland hypothesis
The psychiatrist Rick Strassman suggested that the pineal gland, a small organ in the brain, might produce DMT. It is an appealing idea that has been repeated many times, but that is exactly what it is: a hypothesis, not something that has been demonstrated. Strassman himself also presented it as speculation. More about him in Rick Strassman.
Dreaming, birth and dying?
On top of that, there are bigger claims: that the body's own DMT would be released during dreaming, at birth or at the moment of death, and that this would explain extraordinary experiences. These are wonderful stories, but there is no solid evidence for them. Anyone who presents them as established fact goes well beyond what science actually shows.
What we do and do not know
Honestly summarized: the fact that DMT occurs in trace amounts in the body is a serious research topic. The dramatic stories around it are not, that is for now imagination with a scientific edge. It may fascinate, as long as you keep the distinction between indication and certainty intact.
If you want the basics, what DMT is, then read what is DMT. This article is educational and informational, not medical advice.