Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern about Marley.
Several thoughts come to mind as to why she might behave this way especially given her age and the fact that she otherwise doesn't seem to be bothered by these episodes:
1. If she chews on rawhide or other similar "rough" objects or eats grass or ingests anything which might irritate the back of her throat, then she may develop mild inflammation there which causes this behavior.
2. If she has post nasal drip (for whatever reason), then she may be clearing her throat as the mucous flows down the back of her throat.
3. She's a little on the young side to have anything serious such as collapsing trachea but I'll include it on the list to be complete.
If you think #1 might be the problem, then removal of any offending objects from her may be sufficient to solve the problem and/or preventing her from eating grass, if she does.
If you think #2 might be the problem, then otc Benadryl can be given to help dry up secretions but sedation can often be seen as a side effect. I'm not sure if I'd want to make her drowy.
For #3, this can be a challenge to diagnose but an x-ray is a good first place to start.
If the episodes are only occasional, then I might not worry too much about it. One easy thing that you could also do would be to moisten any dry dog food you might feed in water for 20-30 minutes or feed canned, moist food which will not further irritate the back of her throat.
I hope this helps. Deb