Rosie did the exact same thing when she was around 4-5 months old. We kept her in a crate at night, as we had since we'd gotten her. Nothing was new/changed. Just one night I woke up to hear her panting so hard that I panicked! I pulled her out of her crate and checked her from head to toe, she was fine! And a little surprised to see me in the middle of the night I might add. This happened several times over the next week or two before I had my *AHA* moment. I have horrible night sweats and hot flashes so I naturally assumed she was having the same thing. And I WAS RIGHT! I moved her to a much bigger crate and purchased a small fan. Every night I would turn the fan on and aim it right at her. I kept a small bowl of water in her crate in case she got dry-mouth She has never had another episode since! Not even once! Of course, after a month or so, she moved into our bed and sleeps on her side or on her back directly under the ceiling fan (and curled up against mommy). So I really believe that Rosies issue was heat related. I think she got into a deep sleep and over-heated herself. Try the fan thing, can't hurt! Just make sure the cord is hidden out of the way! Let us know what the vet says though!