What is wrong with my grandpa?

i wont to know what is wrong with my grandpa he is in his early seventies and he is having trouble walking standing and sitting he is always falling down . im really woried about him im always watching him at his house because everyone is afraid to leave him by himself. whenever he walks either his arms or legs shake usually the arm on his left side and he tetters it is all i have to keep him from falling over he moves very slowly and he can hardly here and all these symptoms are recent please help me.