Costochondritis: This is a common condition characterized by inflammation of the cartilage that connects the ribs to the breastbone, often causing bilateral rib pain. It can occur without any apparent reason or trauma, making it a likely diagnosis in this scenario.

Musculoskeletal strain: Strain or overuse of the muscles between the ribs can cause pain, especially if the individual has recently increased their physical activity or has poor posture.
Rib osteoporosis: Weakening of the bones in the ribs due to osteoporosis can lead to pain, especially in older adults or those with a history of osteoporosis.
Hyperventilation syndrome: This condition, often associated with anxiety or panic attacks, can lead to rapid breathing, which may cause chest and rib pain due to the increased movement and strain on the chest wall.

Pulmonary embolism: Although less common, pulmonary embolism can cause sudden onset of chest pain, including rib pain, and is a life-threatening condition that requires immediate medical attention.
Pneumothorax: A collapsed lung can cause sudden and severe chest pain, including rib pain, and is a medical emergency.
Myocardial infarction: Heart attack can sometimes present with atypical symptoms, including chest pain that may be perceived as rib pain, especially in women or diabetic patients.

Tietze's syndrome: A rare inflammatory condition similar to costochondritis but involves the cartilages of the second or third ribs.
Sickle cell crisis: In patients with sickle cell disease, a crisis can cause bone pain, including rib pain, due to vaso-occlusion.
Multiple myeloma: A type of blood cancer that can cause bone pain, including in the ribs, due to bone marrow infiltration and destruction.