As/when/if the spirit moves you British clause
Someone does something when they feel it is the right time.
I love home-made food, but I'll eat out if the spirit moves me.
He travels abroad when the spirit moves him.
I have no idea what he will do, he usually acts as the spirit moves him.
It is unclear information about the origin of the expression, but a source says that it came from the work 'The Quaker Doctrine of the Holy Spirit' in 1959.
Used to imply that someone is acting as if he or she is demure, innocent, sincere or reserved but they may be not
Don’t be fooled by Jennie's good behaviour. She looked as if butter wouldn't melt in her mouth.