In an older patient, these symptoms are signs of a stroke and require immediate medical attention. However, in a younger patient, orthostatic hypotension is the most likely cause. Orthostatic hypotension occurs when a person rises to a standing position from a lying or sitting position and is a result of falling blood pressure. The symptoms are a result of insufficient blood flow to the brain and typically include dizziness, light-headedness, temporary blindness, body dissociation, extremity tingling, or even fainting.
You can read more about orthostatic hypotension here:
You should be evaluated by your primary care physician for laboratory tests and a physical exam to determine what exactly is causing your symptoms.