This is fascinating. I've never used DMT in any form, and have had little experience with other entheogens, but I think I've experienced the same cold spells numerous times over the last 7yrs. It started with an opening from meditating on awareness and it seems as if every time I face and transcend something in myself via awareness that I get very cold, sometimes for several hours even on a hot day, I usually take a hot shower. This has happened, I don't keep track but to guess maybe 15-30 times over the last seven years. I have been attributing it to an effect of a portion of the ego dying. It's said to have once happened to Ramana Maharshi and he was cold and motionless for like a day or more if I remember. I think I've always been sober when this happened, I rarely smoke ganja or do anything else. My intuition tells me it's the same phenomena though. I will start taking aya and maybe doing some extracts and changa before to long, will be interesting to see if I get the same effect as from awareness.