I had a GSD with DM. Those symptoms do not resemble that to me. He started getting a little weak and wobbly in his back legs and when he walked, the tops of his back feet would go on the ground first, (a classic sign) then they'd straighten out. It is a thing where the myelin covering, an insulation of sorts along the nerve pathways gets a tear in it or hole and the electrochemical impulse sort of leaps out and the message isn't continuing along the nerve cells, sort of like the covering over electrical wires tearing and you get a short. The message is more of a spinal thing, not a brain originated thing. Anyhow, he gradually lost more and more control of his muscle movements in the back and back legs mostly. It is not painful but the poor dog got so frustrated because he felt fine otherwise, energetic, wanted to play with the kids but got so it was too much trouble for him. Over the course of about a year, he lost bowel control too and couldn't go up the stairs. There was no sickness otherwise, no throwing up or anything. He was alert, normal in every other way.There is a relatively inexpensive DNA test you can do with a simple cheek swab for DM (degenerative myelopathy) . I am not 100% sure of the symptoms, but every time I read these threads, I think that if this were my dog, I would want to rule it out. It can be ordered at OFFA.org. you can read up about it there too to see if any other symptoms might be the same.