Spontaneous

Adjective

1. Self-generated; happening without any apparent external cause.

   "He made a spontaneous offer of help."

2. Done by one's own free choice, or without planning.
3. Proceeding from natural feeling or native tendency without external or conscious constraint.
4. Arising from a momentary impulse.
5. Controlled and directed internally; self-active; spontaneous movement characteristic of living things.