Don’t so quickly discount mystical descriptions of dreams, even if you aren’t a religious person yourself. The thing that is special about dreams is that unlike our conscious waking experience you have no control over how they manifest themselves. They aren’t scientific or rational at all; they are human. Dogs have dreams, and we wouldn’t expect them to have a rational, non-mystical explanation for them. In a sense your dreams are the only way your body can communicate unconscious (and therefore irrational) fears or desires, short of a panic attack or mental breakdown.

Your fear of snakes is likely older than humanity itself, so even if you can have rational control of yourself around a snake in real life they could terrorize your dreams. Snakes used to be a real and present danger in our environment for millions of years of our evolution. They are the unknown environment, the cunning adversary, the unforeseen consequence of carelessness.

In a similar way, you might find that you can manage to present yourself in social situations, there is a very human fear of being found out, cast out, laughed at, and/or rejected socially, since we are social creatures. Even nudists have dreams of finding themselves naked in front of their peers. If you spend your day putting on a facade of some sort, which you probably do if you have a job, then somewhere there is a part of you that you don’t want others to see, and in your dream they all see it big time and you have to deal with it.