Spontaneous

добро́волен

dobróvolen

(done by one's own free choice, or without planning)

непри́нуден

neprínuden

(proceeding from natural feeling or native tendency without external constraint)

при́роден

príroden

(produced without being planted or without human labor)

спо́нтан

spóntan

(self generated; happening without any apparent external cause)

спо́нтан

spóntan

(arising from a momentary impulse)