I'm experiencing an "off cycle".breath, like a half yawn that's happening involuntarily. what could be causing this?

Fatigue?: Maybe your are tired or very bored. There are some other conditions like a brain tumor or ms or seizures, certain meds, heart attacks but you are not describing any other symptoms. I would try taking a nap. If the sx worsen go see your doctor.

Unusual: I have not heard of this before. It is an unusual question for me. You may be describing hiccups? To get a good answer, you need to be seen by a physician for a full evaluation. Be sure to take some short video clips of these episodes.