Both Uses

spontaneous
in
I Know Why the Caged Bird Sings
(Auto-generated)

Maybe for the sake of business arrangements she restrained a spontaneous reaction.†
p. 207.8 *

spontaneous = behaving in an instinctive, uninhibited manner OR happening naturally (without planning or external force)
We were like actors who, knowing the play by heart, were still able to cry afresh over the old tragedies and laugh spontaneously at the comic situations.†
p. 267.3

spontaneously = happening in a natural manner without planning or external force

Definitions:

(1) (spontaneous)
happening naturally, suddenly, or without outside planning or action
(2) (meaning too rare to warrant focus)