My 11 year old standard schnawzer keeps standing in one spot with his back slightly arched. Whenever I try to get him to move he stumbles and loses balance. He can still get from place to place though. We just had him eat prunes after he stared at them for about an hour. He can still keep his eyes open and he is breathing right. He is drinking a lot of water and now he's staring at the ground again. Any advise?