Rescue dog behaviors

Question
Hi Kristin,
I rescued a dog (malti-poo) from a high kill shelter 8 days ago. He was surrendered at 6 mos. (landlord probs) and then adopted for 3 years in 2005 and surrendered again on June 27th of this year, so he's about 4years old.
Since his background has lots of blank spaces, I don't know why, when I walk him, he will stop and just sit and not allow the walk to go on. This happens all through a walk.
Also, he contorts his body periodically, either after sleeping or after barking and starts breathing really heavily. I think this is reverse sneezing from my research, but am not sure and it's scary to watch.
Can you address either of these issues?

Answer
What you can do for the walking problem,is to try and encourage him to walk,with a treat that he really likes such as small pieces of hotdogs,and try to coax him with your voice and talking softly to him,in time he will learn to walk on a leash

As for the problems with him breathing,that would be best disgusted with your vet,as I'm not qualified with medical questions