Our 7 year-old has recently gone through something like this. Unfortunately to life circumstances, he has had a very stressful life and is continuing to adjust. First, he started to blink his eyes very frequently and often harder than normal blinking. At first we thought something might be wrong with his eyes but when asked he would say that they felt like he had just woken up. We guessed that it might be an attention seeking behavior or related to stress so we would remind him when he was doing it and tell him to close his eyes softly. He could do it as frequent as he liked but not to blink so tightly. Then sometimes when I noticed him doing this blinking I would continue to talk with him but start to exagerate the blinking myself. He noticed immediately and would get a little upset at me blinking too. That passed in a week or so and then he switched to sniffing like he had a runny nose and wrinkling his nose. We would have him take time outs or send him away from the table when he would repeatedly and constantly be doing this. That behavior has now passed after a few weeks and now he is in the hitting other kids at school mode. Trying to teach him better ways to deal with life. Think that your childs behaviors are not physical but more mental or control related. However, like the first advice, give it some time and then consider consulting a physician.
I have been going throught this with my 5 yr. old son, off and on. He started with this tick where he would lean his head over to his left shoulder. It was so odd, and I was so worried. We just had a new baby and he was getting ready to start kindergarten. He worked out of it himself. I would play it off by asking him if his neck hurt. He would say no, but then I would touch it and say "wow, you have a big knot here, let me rub it" So, I rubbed it for 2 weeks, then he said "It feels better now, and he quit." Now, he is licking his lips, which is also a nervous, anxious, habit. I try to bring that to his attention, and he has just started doing something similar with his eyes. I feel bad....I don't think a 5 yr old should be stessed out. Our life is very stressful. I work full time, and have a newborn and also a 2 1/2 yr. old...who is taking a lot of time. I am going to probably have him see someone, who can help him learn a positive way of dealing with stress.
This symptom is likely not related to anxiety. It may represent a motor tic, or it may be related to some rather minor irritation that is not readily observable. For now, I wouldn't seek additional evaluation. Observe it for a bit - it may well resolve spontaneously. Certainly don't draw attention to it.