Benign Paroxysmal Positional Vertigo (BPPV): The sudden onset of vertigo and nausea with head movements is highly suggestive of BPPV, which is a common and benign condition.

Meniere's Disease: Given the patient's history of intermittent left-sided tinnitus, Meniere's disease is a possible diagnosis. This condition is characterized by a group of symptoms, including vertigo, tinnitus, hearing loss, and ear fullness.
Labyrinthitis: This condition, which is an inner ear disorder, can cause vertigo, nausea, and tinnitus. The patient's history of iron infusions may be unrelated, but it's essential to consider all potential factors.
Vestibular Migraine: Although the patient does not report headaches, vestibular migraines can cause vertigo and nausea without headache. The history of iron infusions might be relevant if the patient has a history of migraines.

Posterior Circulation Stroke: Although less likely, a posterior circulation stroke can cause sudden onset vertigo, nausea, and tinnitus. It is crucial to rule out this life-threatening condition.
Multiple Sclerosis: This condition can cause vertigo, nausea, and tinnitus, especially if there are other neurological symptoms. The patient's history of iron infusions might be relevant if there is an underlying condition that increases the risk of multiple sclerosis.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain can cause tinnitus, vertigo, and hearing loss. Although rare, it is essential to consider this diagnosis due to its potential impact on the patient's quality of life.

Superior Semicircular Canal Dehiscence: This rare condition can cause vertigo and nausea, especially with loud noises or changes in pressure. The patient's symptoms might be related to this condition, although it is less likely.
Cogan's Syndrome: This rare disorder can cause vertigo, tinnitus, and hearing loss, often accompanied by eye inflammation. The patient's history of iron infusions might be relevant if there is an underlying autoimmune condition.