Breathwork is a powerful modality to release trauma in the body. It can often stir up traumas in the body to be released. Sometimes that comes with remembering past traumas to process them or seeing them from a newfound healing perspective to free yourself from holding onto it.
Ultimately, you know yourself best. If you are in the middle of something that is very traumatic for you right now–I would suggest not starting breathwork and going to a therapist first. Breathwork may be a good fit for you to integrate what you uncover with a therapist later once you are no longer in the middle of a severe emotionally traumatic event.
If you are concerned about what breathwork may bring up for you on an emotional level, I recommend doing your first session breathing in through the nose and out through the nose in a circular connected conscious way and seeing how that goes for you.
As always, you are in control of your journey. At any point in your journey, you may slow down the pace of the active breath, return to your natural breathing, or lengthen your exhales. Within 5-10 minutes of breathing normally again, all sensations that you are experiencing will mellow out.