The exhibited behaviours are episodic glossolalia, collapsing, fainting, trembling, jerking, convulsing, contorting, and shaking. The individuals performing these episodic behaviours report experiencing overwhelming emotions of love, peace, ecstasy and euphoria. The exhibited behaviours are inconsistent with the claimed emotions, so perhaps another way to understand the question is to explain why individuals behave in a manner that is inconsistent with their emotions. Examples of behaviour associated with euphoria do not generally include glossolalia, collapsing, fainting, trembling, jerking and shaking. The exhibited behaviours are more congruent with the emotions of stress, anxiety, fear, and confusion.
The adoption by some Christian sects of the exhibited behaviours, and other behaviours such as laughing and drunkenness, appears to be relatively recent with the "Toronto Blessing" in the 1990s appearing to be significant. In all cases exhibited, the behaviours and emotions appear to occur in the presence of, and behest of, a charismatic and captivating authority figure.