Excellent question. Subtle problems early on can be very misleading and indeed, can confuse docs. Some common early signs include loss of vision in one eye, weakness in legs or arms, electrical shocks on flexing neck, gait imbalance or incoordination, numbness or tingling, vague persistent fatigue, even confusion or disorientation. Mri's are commonly helpful.
A short list. Visual loss with pain on eye movement, red color desaturation, weakness usually on one side of the body with tingling/numbness, a band-like sensation around 1/2 your chest or abdomen, an electric shock sensation when you touch your chin to your chest are some common signs of ms. None of these signs is diagnostic of MS either in isolation or in combination unless separated in time and space.