Final answer:
The most common position of comfort for a patient with nontraumatic chest pain is sitting upright as it tends to facilitate easier breathing and pain alleviation.
Step-by-step explanation:
The position of comfort for a patient with nontraumatic chest pain is most commonly sitting upright. This position generally allows for easier breathing and can help alleviate pain. Other positions such as lying flat on the back, being semi-reclined with legs elevated, or lying on the left side may be used depending on the patient's condition and comfort, but sitting upright is often preferred.