What Causes Extreme Fatigue,tremors In Hands And Feet Along With Dizziness?

My 25 year old daughter in law has recently experienced episodes where she experiences tremmors, shaking hands, tingling senstaion of hands and feet, tender muscles in back of legs, low grade fever of 100 off and on - lies down for a few hors and feels better) , has exteme fatigue - cannot get enough sleep, episodes of studdered speech,or inability to speak clearly, trouble conentrating and faintness/dizziness. These episodes have just started suddenly over last two weeks. Blood work came back normal - no indicatoins of autoimmune disorders no infections