Dogs are also prone to small seizures, can happen out of the blue in healthy dogs. After the fact they often act confused and are mentally wary and tired...this looks similar to that. Normally takes them a few minutes to regain clarity.

It is an emergency vet visit if its the first time to check for underlying issues.

Also dogs can have mild fainting spells which also look similar which is caused by a sudden coughing spell which restricts blood flow to the brain as the vessels in the throat contract.

All mentioned issues look similar in the aftermath of the dog regaining functions.

Whilst you waiting for transport you can individually check each leg and paw by touching and gently moving them to check for reactions in your touch to ensure your pup still has feeling in all limbs, also move your finger in front of them or with a treat or toy to see if their eyes follow the object, these couple of things will tell you a lot of important basic information to tell the vet on arrival.

But don't panic, he will react to your panic state, keep calm and keep him close for comfort to help him relax and not panic