I don’t have an original attribution, but someone once said that a good volley motion is similar to catching a baseball. A fielder does not swing their arms towards the ball. The arm is extended outward to place the glove in a position to intercept the ball. Instead of a baseball glove, perhaps a Lacrosse stick is a better visualization. Think of the racquet face as something you might use to simply catch the ball. There is no need for a swinging motion as the ball’s momentum will supply sufficient power.
For isntances where you want to supply more power to volley a softer shot, use shoulder rotation to move the racquet towards the ball, keeping it positioned in front of you.
You can practice this technique by having someone feed you short balls and catch them with your hand. Think about duplicating this motion with an actual volley and it may help you overcome that swinging instinct that leads to inconsistency.
Good luck with the game!
The Algorithmist 