Is sleep walking something you either do or not?

Like everything else: We either do or do not do everything in life. The difference is whether we control doing or not doing things or don't control them. By definition sleep walking is involuntary. Other types of behavior done in our sleep exist that are also involuntary such as sleep talking and sitting up with night terrors.

Yes: I never had any sleep walking in my whole life.

Sleepwalking: Sleepwalking can happen in the deepest stage of sleep called delta or slow wave sleep. It can be genetic but may happen spontaneously or may happen in sleep apnea or by some meds like Ambien (zolpidem) etc. Please ensure safety so there is no bodily damage.

Sleep walk.: One theory is that the cause is a delay in maturation of the central nervous system. Other possibilities include genetic predisposition, excess tiredness, sleep deprivation, fever, other sleep disorders such as restless legs, or medications.