You don’t need to worry for tremors of few seconds. It could be because of fatigue or muscle overuse like holding pen or even using thumb for typing on mobile.. lack of sleep or over drinking of tea and caffeine can also cause such small duration tremors. Try avoiding all these. And precautionary get your vit
B12 , serum
calcium, vit D and
thyroid profile done. R u taking some medicines on regular basis ? As Some medications and nerve compression also can also cause this.
Next Steps
Contact me or any physician if the tremor is increasing in duration or it involving more muscle than thumb with all your reports