a conflict i have with my Pawpaw (my granddad)

The thing about my pawpaw is he nice some days mean the other and I don't really mess with people that act that way because its doing to much in my opinion. either you gone be nice to me all the time or not at all.  he don't know how to just be nice I really believe that he is bipolar or his old age is just getting to him. for example : at my grand mom house I go in the kitchen and get whatever I please at any time . okay with that being said I think something goes off within him to tell him that somebody is in the kitchen. I promise you every time anybody not just me anybody walks in there . here he come down the stairs yelling asking who in the kitchen and talking about we always eating up all the food blah blah blah but on the other hand he be the main one in there but don't nun of us care about it like he does . then 2 hours later he will come and ask you if you want some to eat like BOY YOU DONT GONE!!!!