Could brain damage begin as weakness in legs and body twitching? those were my first signs before the memory, cognitive problems, pers change began?

Unlikely at your age: Unless you had a serious head injury in an accident or had previous vascular condition like very high blood pressure or seizures or any neurological condition; these symptoms could be due to fatigue or depression or boredom. You can see a psychiatrist to determine the cause of the symptoms after providing more details of your life events and style of living to the evaluating professional.