My muscles/nerves sometimes twitch rapidly. is this an early sign of something like muscular dystrophy or parkinsons coming later in life?

Not likely: I remember worrying about my muscle twitching as a young man. Neurodegenerative disease unlikely. It seems that we all twitch from time time, with little focal areas of fasciculation. 50 years later and I'm still not degenerating since my first concern (I think). Not the case, however, if accompanied with weakness, pain, or reduced sensation, in which case you would merit a neurologic eval