Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 16 years of experience. I look forward to working with you.
This sounds very suspicious to perhaps be caused by myasthenia gravis, which is an immune mediated condition. The most common symptoms include all or some of these: exercise-induced weakness, fatigue, pelvic limb weakness or stiffness, megaesophagus, reduced gag response, voice change, neck weakness, and facial weakness. You will need to work with your veterinarian to diagnose this. The easiest way to diagnose is to submit a blood test (acetylcholine receptor antibody test) or some veterinarians still do the older way which is a tensilon test. Treatment is tricky, especially in the younger dogs but there are certainly some medications that can be used that will improve the situation.
Another possibility is a muscle cramp which can come from a variety of problems and general screening lab work to look at glucose and electrolytes is important.
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