When it comes to the breath, we will often think of ourselves as breathing. However, the reality is that we are being breathed. In the classes that I teach, this is often a surprise to the participants as a result of long standing attempts to control the breath, often undertaken without our direct knowledge.
Try stopping for a moment and notice your breathing. Notice whether you have any sense of controlling the breath by pulling the breath into the body and/or pushing it out. if this is the case, let go and see if you can simply let the breath come in and out without trying to control it. It is important to be patient as it may be quite subtle to distinguish between you breathing versus being breathed by the breath.
One way to make it easier is to after you let the breath go out, allow for a pause and try to relax and wait for a few moments. Next thing you know the breath will come in without you purposefully providing the energy.
I like to quote one of my favourite meditation teachers, Sharon Salzberg, who suggests that our breath is and can be treated like your best friend. It is always there and it constantly moves in and out of the body over our lifetime. The breath can serve the purposes of bringing the mind into the present moment and it can become an anchor for our attention to an aspect of our experience that is happening in the here and now.