Explanation for the "spinal energy" and other "Kundalini awakening" symptoms?

Lots of people have been uploading videos and sharing testimonials describing the symptoms they have experienced during episodes of the so-called "Kundalini awakening". The Wikipedia article on Kundalini says the following on the matter:

The Kuṇḍalinī experience is frequently reported to be a distinct feeling of electric current running along the spine.[8][9][10]

Similarly, Marjorie Woollacoot, PhD and professor of Neuroscience and Human Physiology at the University of Oregon, states the following:

[…] it is amazing that it is that common, where a person may not even have heard of these things before to suddenly feel this energy moving up their spinal column, from like the base of the spine to the crown of their head. And then also subsequently feeling energy in these different centers as they begin to notice transformations in their life. Feeling electrical energy, feeling heat, feeling light, and so often it is associated also with the sense of joy, and like absolute bliss that they are amazed about […]

A convenient place to find lots of testimonials on Kundalini awakening is the subreddit on Kundalini, which has been in operation for over a decade. Below a quote from a recent testimonial:

She [the OP’s mother] had been meditating for several year and focusing on the middle point of her forehead while meditating.

A few weeks ago, she experienced the awakening and has been feeling a constant flow of energy flowing throughout her body. She describes it an energy that rises up and almost wants to “lift her up” and is something that’s overall overwhelming/unpleasant. She is currently unable to read/meditate/do her breathing exercises without feeling overwhelmed by this energy.

Similar stories are available in video form on YouTube as well. Below some examples:

In 2016 I went through a massive Kundalini awakening that shook my entire life. Everything felt like it was just collapsing so hard, and I had no idea what was going on. I felt the energy shoot up on my spine and it burned. It burns and I hadn’t felt anything like that […] (source)

[…] and then all of a sudden, sitting there, feeling so despondent, I had this crazy tingling start at the base of my spine. Then it got warmer and warmer and warmer to the point that it was freaking hot, like someone was freaking stabbing something into my back [laughs], and I was like what is this? what is going on? It was so uncomfortable. I started moving around and like trying to get it out. And then it kind of chilled out a bit, and […] I could feel like this swirling, like these two – what I know now are "nodies" – like swirling around. And all of this energy just engulfed my hips and like getting into all my organs, and then it started moving up and up and up and up, moving through all of my chakras. And, bear in mind, I had no idea what Kundalini was at this point […] so it moved up and up and up, and like got stuck in my throat for a while, and I don’t know how long this was happening, but when it got to my crown … it was just like boom! fireworks, sparkly freaking fireworks coming out of my head […] and it was so euphoric! It was so awesome, I just felt … I can’t even … the English language is so limiting […] (source)

[…] so those of you who are unfamiliar with the idea of a Kundalini awakening, it’s where a large amount of energy is released from lower parts of your body and moves up to your crown and out of your crown chakra, and, at the time I had no idea what a Kundalini awakening was. I’d never heard of one. The situation was, I was at a Buddhist lecture with my friend and we had just gotten finished with the lecture, we were sitting in her car and I started to feel a little strange. She went into the grocery store to get something and when she came back is right when it started to happen. And, initially the feeling was like this vibration, like sort of like my butt cheeks were asleep, it was a vibration at the base of my spine, and it kind of started growing in intensity. So I paused and I turned to my friend and I said "something it’s happening". That was the last thing I was able to consciously control coming out of me, because at that point then my body started to like freeze up, my arms and my legs went out in front of me and like tightened up, and the energy continued to grow and then began moving up my spine, I could feel it moving up into my intestines and my stomach, into my chest. And it was like, it felt like the feeling as if a body part was asleep and has that like really intense vibration feeling, but it was like swirling, and I could feel it swirling around. And then it got to my heart, there was this big release of grief and at the same time like ecstasy? So I felt really sad, I started crying, and then I also was really happy, I felt like this bliss. It was the weirdest sensation because it was so conflicting. I was also real scared, haha, so I was having this intense emotional experience and then also feeling fear because I didn’t understand what was going on […] (source)

What is the explanation for the symptoms people commonly report to feel during "Kundalini awakening" experiences, such as energy rising up through the spine, vibrations, electric currents, heat and sometimes even euphoria/ecstasy/bliss?

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Update: I found this article suggesting an overlap between panic attacks and Kundalini awakening experiences. However, some symptoms, such as the experience of ecstasy or bliss, are not part of the overlap, indicating that there is more to the experience than just a simple panic attack.