Eye twitching may be caused by overusing your eyes. When you overuse your eyes, the ocular muscles will twitch instinctively, hence causing eye twitching. Usually, eye twitching is caused by the increasing nervosity of nerve fiber in charge of ocular muscles. Eye twitching when you yawn is sporadic and do not need to take medicines, such symptom will relieve and disappear after taking a good rest.
Since you are not nervous or tense, the problem may not be so serious. The twitching eyes must be caused by the not hygiene condition. There must be the sands or the dusts in your eyes. You could use the eye drops to release the symptom now and then see whether it is released.