Is it a tic or a fasciculations? Fasciculations are sometimes called tics, but they are different. Fasciculations are usually just one small muscle having a spasm, like an eyelid twitching, or a pulsing of a leg muscle. These can be cured over time by taking a magnesium supplement, as it's usually a lack of magnesium that causes the muscle to spasm like that.
An actual tic, like what people with Tourette's have, would be of neurological cause so it might be worthwhile to see a neurologist.
Either way, I don't think the Zyrtec is causing it.