Mine shuddered on take off all the time when it was stock. Started after about 100 miles. It was a major concern for a long time. Other people on here with People 50s have complained about the same thing. Mine also had a funny noise at just above 30mph. Both symptoms stopped when I changed the variator, rollers, and clutch springs. Unfortunately I did them all at the same time so can't tell you what resolved the issues. The vibration could have been residue on the clutches, like wordslinger said, as I did take some light grit sandpaper to them. Also cleaned the bell out with brake cleaner.
