autoasphyxiation
Self-strangulation; a character asphyxiating themselves. Might be achieved with a character putting their_hands_on_their_own_neck, or by placing a plastic bag over_their_head.
May be done for humor. Conversely, make pertain to themes of suicide or imminent suicide.
For autoasphyxiation done for sexual gratification, see autoerotic asphyxiation.