Pick a number from 1 to 5, and raise your left index finger that many times. This is literally child's play.
Introspection reveals little about the underlying process.
Indeed, one's mind can seem eerily blank, giving the impression that the finger is moving on its own. In this case there is no discernible lag between a decision to move the finger and the ensuing motion. Of course, intuitions of 'directness' may be misleading. When a person moves a bodily part, the motion is caused by muscle contractions. The muscle contractions are in turn caused by certain biochemical events in the person's nervous system.