You can have the flu without all of those symptoms, but you know best as far as what you felt you had, regarding the cold.
Weakness and shakiness can indicate an electrolye imbalance. Are you taking medications for anything? Often people get electrolye imbalance if they are taking diuretics or blood pressure medication, sweating excessively, or having nausea and vomiting.
You are also right that an increased blood sugar could make you feel lethargic and shakey.
Arsenic or mecury posioning, antidepressants and lithium, certain antipsychotics can also cause shaking.
So if you are on any medication, let me know what they are.
There are also more severe illnesses that effect the central nervous system such as Multiple Sclerosis, ALS, Parkinson's disease. Let hope it is not anything that serious. The only way to tell would be to see your physician for testing, and possibly a neurologist depending on the type of shaking you are having.