[Sheenagirl]

A vet visit would be in order.
Time for a full blood workup and physical.
At eight years old your boy could have arthritis, etc. Do you give any supplements?
IMO the warmer weather would be better if he does have arthritis.
At eight years old my Sheena still acted like she was four or five.
I do believe a lot of our Rotties sleep most of the day away - mine did!!
Not sure about male vs female (which lives longer) just depends on genetics, health issues, etc.
Good luck on your move!
Let us know what the vet says...