On (one's) own volition spoken language prepositional phrase
If one does something on their own volition, they do it because they want to.
He kept saying that he did it on his own volition, but I know someone told him to do it.
No one told me to give up cigarettes. I give it up on my volition.
It's not because I've done something wrong. I just left the company on my volition.
He'd gone to the police and confessed himself on his volition.
It was often said by a photographer when he would like small children to look at the camera and smile before he took a photo.
When the photographer said “watch the birdie”, all of us looked at the camera and smiled.