Labs are prone to Epilepsy and this usually starts around the ages of 2-5 years. What you may be seeing is a partial/focal seizure. These do not render the dog totally unresponsive as a full blown seizure would but rather you would see behavior changes. Some dogs pace, whine , bark, circle, snap at imaginary bugs, lick air, and there are many other behaviors that can be seen. This behavior can last from moments to days in duration.
I am going to direct you to a site that talks about the different components of seizures. In this site there is a video of a dog licking/ snapping.