Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
The stress of this situation for your sweet Fraser could start a Reverse Sneeze that can cause this in dogs and is related to allergic reactions. This is harmless and will not hurt Fraser. Check this LINK to see if thsi sounds like what this may be.
The other possibility is developing heart disease or Congestive Heart Failure that will cause a harsh cough/retching. It is wise, since you have just inherited Fraser, to have your vet run a thorough physical exam along with lab work to determine if Fraser may require treatment.
I am so sorry for your loss....I know this must ne very difficult for you and for your sweet Fraser.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, XXXXX XXXXX
Thank you so much, Gavin, for your kind rating. It is very much appreciated! Even though you have rated, we can still communicate. If you have other questions, please Reply. I am always happy to help. I hope poor little Fraser does well with your love and care.
Have a wonderful day!