Stress and dryness. You're referring to a 'blepharospasm', which is a flickering of the eyelid that usually resolves spontaneously after a few months. It's almost always caused by stress (including not sleeping well) and dryness. Try using artificial tears 4 times a day. If it doesn't go away after a few months, get checked.
? Eyelid infection. Involuntary twitches, or myokymia, often result from muscle irritation due to adjacent infection. The eyelids are susceptible to these due to the close proximity of oil glands and muscle elements. Lid hygiene, including warm compresses and topical antibiotic steroid drops or ointment will often relieve this, although it can recur if maintenance treatment is not done.
Blepharospasm. Causes quivering or involuntary contraction of the muscle surrounding the eye. This can be a significant problem and often can be relieved with Botox injections into the orbicularis muscle under the guidance of an ophthalmologist or neurologist experienced in the use of the medication. The drug induces a reversible paralysis of the muscle making the contractions significantly less.
Various Reasons. This could be due to an electrolyte imbalance like low calcium or potassium. It could also be due to stress or anxiety. Could also be from caffeine, medication, exercise or lack of exercise.
Diaphragm. If you have started into an aerobic program and notice this pain it could be spasms of the diaphragm. This is a large muscle in thelower torso which can become overworked if just starting on a new aerobic program. If it does not get better over a short time period seek medical help to find out what is going on.