Sudden limb jerking is not a typical side effect of Neurobion Forte. However, since you noticed this symptom after taking the tablet and stopped it, you should not restart it without speaking with your doctor. Limb jerking when falling asleep can sometimes be a normal sleep-related movement, but it can also have other causes, so the timing does not necessarily mean that Neurobion Forte caused it. Your doctor can review your symptoms, other medicines, and vitamin levels before deciding whether you need supplementation. If you have confirmed vitamin B12 deficiency, a B12 supplement only may be suitable, depending on the cause and severity of the deficiency. Do not switch to another supplement without medical advice. Seek prompt medical attention if the jerking occurs repeatedly, happens while you are fully awake, or is accompanied by weakness, loss of awareness, or other unusual symptoms.