Many who have experienced the Kundalini have had great difficulty with it. Much of that is brought about from the inability of the person to surrender to it. By not surrendering they resist and in this resistance comes fear and from fear can come pain. Or MDs force pharmaceuticals upon the awakening person causing much anguish and sometimes a "burning" as the Kundalini will continue regardless of the chemical blockages.
The fire aspect is related to the heat one can feel. Fire and snow hot and cold aspects come alive with Kundalini. Sometimes when a person is under the sway of drugs or inside of an awakening from a Kundalini Guru who isn't so concerned about the welfare of the disciple an intense form of Shaktipat can occur which can burn. Leaving red scorch marks on the spine or top of the head. I did this only once before the safeties came about.
Other times the release of Kundalini from a traumatic accident can "feel" to the person like they are burning but with no flame. And then much of the visions given from the Kundalini are of a quality of light. Such as the "enlightenment" which can be so bright as to require only the briefest flashes of it to make itself perceived.
Shiva (sacred male) representing the right side of the body is concerned with heat and fire among other things. And if a person pursues only the right side they will experience heat, sometimes MUCH heat. Patrilineal organizations will often pursue the "male" aspect at the sacrifice of the female and this can be a very unfortunate mistake with Kundalini. So a balanced approach is best.
Another symptom of Kundalini for a few is the spontaneous fires that erupt out of nowhere. These are the true pyrokinetics. St Theresa of Avila was one of these though there are many less celebrated ones. They quickly learn to hide or the Kundalini adjusts to those individual situations.
Most of the dire and unfortunate experiences come from people storming the gates of heaven without being willing to surrender to those very gates. People who are in such a hurry that they will burst into the Kundalini with no preparations. There are many of these people even at this very moment. Some will go insane as the fear that they inject from the symptoms of resistance can be overwhelming. Some will suicide as their struggle puts them into a deadly spiral of fear and depression.
So the Kundalini gets the blame as a dangerous practice. And it is for those impatient, fearful and unwilling to "come as a child". Preparation and surrender and patience are some of the main components of a safe and joyful experience.
Kundalini flies in the face of some religions as well. So there has been some programming to steer people away from exploring this aspect of their natural God given selves. Kundalini is as much a "spiritual event" as it is a "mental event" "psychological event" "emotional event" and a "physical event". Being so it has the potential to release truths that do not conform to some of the programming that has been insinuated. So there are problems with some of the organized belief systems as well and they will steer people away from it. Even so, all roads lead to the great path and all eventually will walk this path.
So these are merely some of the reasons that people have difficulty with the Kundalini. Yet with knowledge comes power and with grace comes the ability to discern how to use it. - blessings - chrism
Most of the dire and unfortunate experiences come from people storming the gates of heaven without being willing to surrender to those very gates.