I have a 6 yr old that I have to draw a line to see if she moves!

Unless it's meal time or someone comes to the door, she just lays there and sleeps mostly. She does not play with the other dogs or toys at all. I don't know if she was ever any different b/c I got her only a few months ago. Her previous owner said she was always like this. She is healthy and is a couch potatoe! I used to think there was something wrong too but this appears to just be her personality, so unlike my others, the rest of the gang is constantly on the go, even the 8 yr old, go figure....