By your description, this sounds like "orthostatic syncope" (fainting spell due to sudden drop in blood pressure and inability to perfuse the brain). When one stands up, gravity tries to pull everything down, including blood. If the blood vessels don't clamp down quickly enough, you can have a decrease in the amount of blood getting to the brain. When the blood pressure drops below a certain threshhold, your brain doesn't get what it needs and you pass out. The eyes being rolled back and fluttering is commonly seen when people have syncopal events (i.e. fainting spells). With fainting spells, they typically last just a few seconds, and the person returns to normal (in terms of alertness, interaction, etc.) very shortly (seconds to a couple minutes) after the event. Seizures tend to last longer--several seconds to 2 or 3 minutes (sometimes very long); and most people are tired or disoriented/confused or agitated for several minutes (15, 20, 45, etc.) afterward.

The lip smacking in your sleep could just be benign. Lots of people do "unusual" things in their sleep (talking, walking, kicking, hitting others, etc.) People with anxiety not uncommonly have "unusual" movements in their sleep too.

Is seizure a possibility for what happened to you? Yes. Is it the most likely thing? Not really, based on your description above. The description you gave is very classical for orthostatic syncope. If it's orthostatic syncope, staying hydrated and eating enough is important. If you were to continue having such spells, your doctor may want to check you for adrenal gland dysfunction or anemia, etc. But we all experience "orthostatic presyncope" (dizziness without fainting upon standing or after standing for a while with knees locked straight, etc.) from time to time. Some people will go on to fully pass out.

I would recommend discussing the spell with your doctor so he/she can at least know about it; and if he/she feels a workup is necessary (such as checking blood pressure/pulses, checking blood labs--or an EEG if he/she suspects seizure) that can be done. You should also go to your state's Department of Motor Vehicles website or call them and ask what the driving restrictions are for people who had a spell of passing out. In some states, even if you didn't have a seizure but passed out, you may not be allowed to drive for some period of time.

Overall, as I said, this sounds classically like orthostatic syncope; but at the very least, I recommend you at least call your doctor to let him/her know about the spell and see if they feel further workup is necessary.