Does methyphenidate have a side effect of muscle tightening that looks like a myoclonic reaction? if so, any way to help that?

Yes;reduce dose: All central nervous sytem stimulants produce myoclonic-like jerks (amphetamines, methylphenidade, caffeine, etc). Check liver and kidney function, since renal and liver abnormalities can induce myoclonus with small doses of methylphenidade. Reduce dose. It would not be fair to add another medicine to control the myoclonus (but Clonazepam can help).

Yes, very possible: Have seen myoclonus rarely with stimulant treatment, depending on the severity of the movements and the reason the med is being used, would consider reducing the dosage first if possible.

Not exactly: Methylphenidate commonly cause tics which are quick, uncontrollable movements. A common tic with methylphenidate is blinking the eyes very frequently to the point it is bothersome or the person is embarrassed by this. Sometimes the tic doesn't go away after the methylphenidate is discontinued. The tic should then be treated with medication.