Can primary cervical dystonia first present only at rest (lying down: initially on l side, later r) and only 18 mos later begin to appear when upright?

Cervical dystonia: Cervical dystonia may present many ways. It's not likely however that it starts by occurring only with lying down, then months later appears all the time. Cervical dystonia may also simply be a pain or impaired rotation in the neck, rather than the obvious twisting or flexion of the neck to one side. What makes you think you know someone who has this condition?

Yes.: Cervical dystonia can present various ways. It can first present only at rest, then later manifest when upright. See a neurologist or physiatrist for treatment.