If finger twitches aren't a result of muscle strain or exhaustion, there's a possibility you could have a deficiency in certain minerals like magnesium, potassium, and calcium, as well as a vitamin E deficiency (via the International Board of Credentialing and Continuing Education Standards – IBCCES). 

Finger twitching can also be an early symptom of more serious diseases, including Parkinson's and Lou Gehrig's disease according to Healthline. There's also a possibility that this could be a symptom of Hypoparathyroidism, which can come with a variety of other symptoms including muscle aches, twitching, and weakness. Tourette Syndrome is also a factor, which involves involuntary repetitive movements. 

If finger twitching is persistent and lasts more than a few weeks, it's recommended that you go to your doctor to check whether this tremor is something more serious than just muscle fatigue or stress. That way, they'll be able to screen for diseases like Parkinson's or Lou Gehrig's and deficiencies in minerals or vitamins and provide you with the appropriate treatment.