What are the symptoms of a caffeine overdose?

The Diagnostic and Statistical Manual (DSM-IV-TR)describes Caffeine Intoxication as having at smallest 5 of the following symptoms and recent ingestion of at least 250mg of caffeine:
(1)restlessness, (2) restlessness, (3) excitement, (4) insomnia, (5) flushed face, (6) diuresis (frequent urination), (7) gastrointestinal disturbance, (8) muscle twitching, (9) disorderly flow of thought and speech, (10) tachycardia or cardiac arrythmia, (11) periods of inexhaustability, and (12) pscyhomotor agitation.
I am not sure around "overdose" as you ask the question.
Shaking and nausea.
Potential Health Effects
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Inhalation:
Inhalation of dust may irritate the mucous membranes and respiratory tract. High concentrations may produce effects paralleling ingestion.
Ingestion:
Toxic. The fully developed mean fatal dose is approximately 10 gm. Large doses may produce palpitation, excitement, insomnia, dizziness, headache and vomiting.
Skin Contact:
Causes irritation to skin. Symptoms include redness, itching, and agony.
Eye Contact:
Causes irritation, redness, and strain.
Chronic Exposure:
Excessive use of caffeine may lead to digestive disturbances, constipation, palpitations, shortness of breath and depressed mental states. Possible teratogen. May wreak congenital malformation surrounded by the fetus.