“What causes uncontrollable eye blinking?”

I assume you mean a rapid, unintentional twitch of the eyelid? That is called, blepharospasm. It is a localized muscle dystonia that could be due to fatigue, on the computer too long, or just plain short out of the part of the brain that switches muscle off n on. You can treat it with botox if it does not simply go away after a bit of rest.