Self-acting

a.

1.

Acting of or by one's self or by itself; - said especially of a machine or mechanism which is made to perform of or for itself what is usually done by human agency; automatic; as, a self-acting feed apparatus; a self-acting mule; a self-acting press.

Adj.

1.

self-acting - designed to activate or move or regulate itself; "a self-activating sprinkler system" Synonyms: self-activating, self-moving, self-regulating

automatic, self-activating, self-moving, self-regulating