Feeling lightheaded or dizzy, is one of the prime symptoms of anxiety. It can be caused by hyperventilating, and one can hyperventilate, and not be consciously aware of it.
Lightheadedness is one of my main symptoms. It can occur at any time, when I least expect it. However, there are also triggers that cause me to experience it If I am driving, as long as the car is moving, I am fine. But if I come to a stop, at a stop sign, traffic light, or going through the drive-thru at a fast food restaurant, panic can come over me, with the lightheadedness.
So yes, you can hyperventilate, and not be aware you are doing it, and many of us do have triggers that can cause panic and lightheadedness.
The very best to you, TSD!... Chuck