I am new to this site and am not entirely sure if this is an appropriate question to ask, if it is not forgive me. I practice Vipassana meditation and after some time observing the breath, I feel the need to take a deep breath in, as if I'm fixing to suffocate and require a large inhalation of Oxygen. This sensation always arises after I really feel like I have pinpointed the breath and my breathing becomes more shallow. It seems to be creating an impasse in my practice, for as I begin to feel the first Jhana arising, my mind immediately shifts its focus to the satisfaction that occurs after I breath in heavily.
If your breath becomes shallower faster than the extent you have calmed down the fabrications this tend to happen. Sometimes the breathing stops and suddenly after someone time you gasp to breathe. But again these inconsistencies reduce after some practice so might be safe not to pay attention to it and keep your focus on the breathing process.
Alternatively you might be trying to control the breath even without your knowledge. You might be "forcing" the breath to be shallow causing a gasp to breathe.
This sometimes happens to me during shamatha meditation. Through trial and error I found the best way to deal with it is to let it happen, let it come and don't resist it. If I need to take a deep breath, I notice the need, take the breath and bring my attention again back to my breathing (minding the breath). At most, what I am experiencing is just a distraction. It could be an itch, a pain, an emotion, and image in my head, a thought, or in this instance, and urge to inhale deeply. So once you notice it, just return to the breath and proceed with the practice.