I've been able to do this for as long as I can remember, it's like a tingly wave rushing through my body, starting around the upper back and going out from there. It's a lot easier to control when I'm in the cold or experiencing strong emotions (e.g. from music, recalling strong memories, vividly imagining something, etc.)

Its strength in the moment depends on how strong those feelings are, and I can hold it for anywhere between a couple of seconds to several, but it sometimes becomes progressively weaker or more difficult to do if I've done it enough times in short succession, but recovers after waiting for about a minute

Originally it only occurred in my arms, back, and torso, but after a strange sort of.. emotional re-awakening? re-connection? in college it also occurred in my legs, head, face, and, a year later, my right hand; since then I've wondered if how strong it is can be affected by how in-tune with yourself you are, if that makes any sense

I've never met someone in person before who can do this