Hi there, the most common causes of lip twitching are stress, fatigue, anxiety, anger, potassium deficiency, excess stimulants like coffee, tea etc, alcohol
withdrawal, cigarette
withdrawal, damage or facial nerve irritation, bell’s palsy etc. causes of persistent lip twitching, are hemi facial spasm, tics and tourette syndrome. Parkinson’s disease can also cause these. You need to consult a neurologist for evaluation. Hope this helps. Take care.