HELP! What does this dream mean???

Date: 8/17/2018

Before I get into what happened in the dream, a little backstory.. my grandpa passed away 3 years ago and my grandma passed 2 years ago. I had a dream last night that I was at my grandpas funeral but instead of a casket he was sitting in a chair at the front of the room. I noticed he started moving. But no one else noticed. He started moving more and more and I just thought maybe this is an involuntary response from his nerves dying but then he opened his eyes!! I freaked out and my grandma was there! I said mammaw! Pappaw is alive!! She said no he’s not! I said yes he is he is moving and his eyes are open! (He was looking around the room) Then my grandma got up in his face to look into his eyes and she said no honey his eyes are open but he is dead he’s not here. The end. Really freaks me out and I just want to get a little clarification on what this dream means. I have been visited by my grandparents in dreams before but they were happy and clear messages. This one was just scary I woke up frightened.