Thank you for your patience. These symptoms your boy had last night are definitely a concern and given his age and what you saw it is quite likely that this was a fainting episode. We also have to consider whether this was seizure like activity, but given it doesn't sound like he was shaking or twitching, then it is very unlikely that this was a seizure event. If this was sycope (fainting), then there are a few common causes, but in a 9 year old dog, the most likely cause would be a primary heart issue. Small breed dogs are prone to heart valve issues, and that could potentially be an underlying issue for your boy. For this reason, I would definitely recommend a full vet check up today or tomorrow if possible. Here they can carry out a full physical exam - but in particular, a careful listen to his chest to see if there is a murmur. An audible murmur would be enough of a reason for further tests (including an xray, ecg or echo (heart ultrasound)). This would likely then be enough to rule a primary heart issue in or out here.
Of course we have to consider other possible causes for your boy's symptoms last night, and this could even include a poisoning or toxicity, or even an allergic reaction (from a bug/bee bite of sting for example). If you can follow up on this with your local vet today, that would be the best way forward. If not, then please keep a close eye on his mucus membranes, capillary refill time and respiratory rate as follows:
Mucus membranes - flip his lip and look at the color of his gums. They should maintain a nice salmon pink color. Get him to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.
Respiratory Rate - if he is continuously panting throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
Best of luck with your boy and hopefully this was just a one off! Given it sounds like a fainting episode however, you are best to play it safe and get him checked over today if you can. I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!
PS: If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. E..." or "Pet-doc..." and others will leave the questions for me.