I got exactly same sensations on mushrooms ( 3.5g cubensis, after 24 fast, in beautiful natural environment). It was most profound experience of my life. As you said, the feeling was so powerful
and that sensation of snake wrapping around spine was so real
It was followed by exactly this vision
https://www.youtube.com/watch?v=7pGV8fTCOGQ , this is something that intrigued me mostly because then i didn't have any knowledge about shared visions among psychonatus.
Anyway, it is amazing that you get those kundalini sensations every time you smoke spice
Mystics say that it is always present at the base of our spine and that it only needs to be activated. There is practice called kundalini yoga which uses some mantras, pranayama and postures to activate that kundalini energy. I have a friend who experienced exactly same thing with kundalini yoga posture where he was saying SAT-NAM mantra in some pose for 2 hours. These practices are very powerful and should be approached with caution because that kundalini energy can do serious harm if the mind and body aren't prepared (i have red it on erowid and in Barbara Ann Brennan's book Hands of light) Also i think that there are many other ways to activate that same energy like prolonged fasting, meditation, dancing etc... Maybe you could activate it with Stanislav Grof's holotropic breathwork, i haven't tried it but people report very profound experiences with that practice. It is combination of prolonged dancing, accelerated breathing, meditating, massage to evoke mystical experiences. Maybe that wouldn't bring kundalini sensations but i think it was worth mentioning .
I wish you all the best with your future trips and kundalini practice and hope it will bring you much love and light in your life