Jackson,
i usually feel the vibrations prior to any "mind-blowing" experience. that's my go signal to ride it out and see what's behind the "door".
thinking back. i can remember feeling all kinds of fear: like fear of death, fear of my loved ones losing me if i get annihilated, but in essence it's more than fear of bodily death. i think it's fear of the ego dissolving into a formless awareness. i also think that this is a deep-seated fear ingrained at a cellular/sensory level (e.g. the reptilian brain acting up its fight/flight response), at least that's my conjecture.
however, during the experience of heat, i wasn't fearful. just curious why it was so hot in herre

the tone was like a high fever. the heat was all over my body but more pronounced on the back of my neck.
i noticed that my experiences got stronger soon as i picked up on my daily sitting practice. however, during sitting practice, there seems to be a "wall" that prevents me from experiencing the same experiences i have during lying down meditation. i think this is due to the more pronounced relaxation of the lying down position, and also, my lack of concentration during sitting practice.
in any case, practice continues...
~C