There are few internal stimulus that can invoke the dreams about the red snakes. Those stimulus can be separated in psychological and physiological types. The latter type includes anything what relates to bodily physical functions, thus a high blood pressure and a high level of heart beats rate are internal stimulus. Those can trigger our subconscious mind to recreate visions of the red snakes. Psychological internal stimulus can be anything related with innate sexual brain work. Thus instinctive physiological processes, like a desire for intimate physical contact or a fear of it, are triggering base of red snake dream.
Read more about dreaming of Red snake in other dream meanings interpretations.