Jeanette is correct it could very well be Hypoglycemia (low blood sugar) that is causing it. It could also mean something else entirely. Signs (what you actually see) and symptoms (what you actually feel) of hypoglycemia.
Here are the signs and symptoms of hypoglycemia: 
Adrenergic manifestations
    Shakiness, anxiety, nervousness
    Palpitations, tachycardia
    Sweating, feeling of warmth 
    Pallor, coldness, clamminess
    Dilated pupils (mydriasis)
    Feeling of numbness "pins and needles" (paresthesia)
Glucagon manifestations
    Hunger, borborygmus
    Nausea, vomiting, abdominal discomfort
    Headache
Neuroglycopenic manifestations
    Abnormal mentation, impaired judgment
    Nonspecific dysphoria, moodiness, depression, crying,  exaggerated concerns
    Negativism, irritability, belligerence, combativeness, rage
    Personality change, emotional lability
    Fatigue, weakness, apathy, lethargy, daydreaming, sleep
    Confusion, amnesia, dizziness, delirium
    Staring, "glassy" look, blurred vision, double vision
    Flashes of light in the field of vision
    Automatic behavior, also known as automatism
    Difficulty speaking, slurred speech
    Ataxia, incoordination, sometimes mistaken for "drunkenness"
    Focal or general motor deficit, paralysis, hemiparesis
    Paresthesia, headache
    Stupor, coma, abnormal breathing
    Generalized or focal seizures
    Dysmenorrhea
Only a doctor can accurately diagnose hypoglycemia (or any other problem accurately) through a series of tests. Other things to consider are age, weight, male or female, familial (family) history, stress levels, other medications, etc. 
In other words you may be fine after eating (curious as to what is your meal schedule) may not have any other symptoms and have hypoglycemia or pre-diabetes. Only your doctor will be able to tell you.  
Though, I doubt Parkinson's, and again only doctors tests will confirm, or even deny; I do know that Michael J. Fox had a problem during the filming of Doc Hollywood. One of his index fingers wouldn't stop twitching. Think it was a pinched nerve he went to the doctor at the conclusion of filming. It took a full-year to properly diagnose Parkinson's.
Since this is rather long - I recommend that you don't wait get seen by a doctor.
Take care,
Stargazer