Orthostatic Hypotension: This condition is common in the elderly due to decreased blood volume, medications (e.g., diuretics, antihypertensives), and autonomic nervous system dysfunction. The symptoms of dizziness and shakiness, especially when standing up, align well with orthostatic hypotension.

Benign Paroxysmal Positional Vertigo (BPPV): A common cause of dizziness in the elderly, related to the movement of calcium particles in the inner ear. It typically presents with brief episodes of vertigo triggered by specific head movements.
Vestibular Dysfunction: Age-related decline in vestibular function can lead to dizziness and imbalance. This could be due to various factors, including inner ear disorders or neurological conditions affecting the vestibular system.
Medication Side Effects: Many medications, especially sedatives, antihypertensives, and antidepressants, can cause dizziness and shakiness as side effects. Given the polypharmacy common in the elderly, this is a plausible consideration.
Hypoglycemia: Low blood sugar can cause shakiness, dizziness, and confusion. Elderly individuals, especially those with diabetes, are at risk due to medication effects or other metabolic issues.

Stroke or Transient Ischemic Attack (TIA): Although less likely, it is crucial to rule out stroke or TIA, as these conditions can present with sudden onset of dizziness and require immediate medical attention.
Cardiac Arrhythmias: Conditions like atrial fibrillation can cause dizziness due to reduced cardiac output. Given the potential for serious complications, including embolic stroke, this diagnosis should not be missed.
Severe Anemia or Blood Loss: Significant blood loss or severe anemia can lead to dizziness and shakiness due to reduced oxygen delivery to tissues.
Infections (e.g., Urinary Tract Infection, Pneumonia): In elderly individuals, infections can present atypically, with symptoms such as dizziness or confusion being prominent.

Multiple System Atrophy (MSA): A rare neurodegenerative disorder that can cause orthostatic hypotension, leading to dizziness and shakiness, among other symptoms.
Pendred Syndrome: A genetic disorder affecting the thyroid and inner ear, leading to vestibular dysfunction and potential dizziness.
Autoimmune Disorders (e.g., Hashimoto's Encephalopathy): Rare conditions that can cause a variety of neurological symptoms, including dizziness and shakiness.