Is the eye condition "strabismus" commonly occasional, and can it be triggered?

Yes and Yes: There are many forms of strabismus that can be intermittent. In kids, amblyopia (lazy eye) is generally less severe or common in intermittent strabismus than constant strabismus. Strabismus often will worsen torwards then end of the day or during periods of fatigure. But certain foods, alcohol, etc. Have been known to trigger episodes of double vision.

Yes: Some types of strabismus can be intermittent. One type is intermittent exotropia, which often is controlled most of the time. The control can diminish and the deviation will occur more often. Another is accommodative esotropia, which is controlled with glasses.