self-acting
1. [ adjective ] designed to activate or move or regulate itself
Synonyms: self-moving self-regulating self-activating
Examples:

"a self-activating sprinkler system"

Related terms: automatic
Similar spelling:   self-asserting
  self-sealing
  self-examining
  self-assertion
  self-giving
  self-serving
  self-seeking
  self-assertive