Brief Answer:
Mostly benign, get evaluated if persists for more than a week

Detailed Answer:
Thank you for asking

I read your question and i understand your concern. Lip twitching although looking worrisome most of the time is self resolving and is due to benign conditions. Commonest causes of lip twitching are
Stress.
Fatigue.
Severe anxiety.
Emotions, such as anger, amusement, fear.
Potassium deficiency.
Excessive stimulant intake – coffee, certain soft drinks, tea, chocolate and over-the-counter (OTC) stimulants.
Alcohol withdrawal or abuse.
Cigarette or nicotine withdrawal

apart from it, if the symptoms persist and do not respond talk to your neurologist and let them rule out some other less likely neurological causes like facial nerve involvements, tics, hormonal imbalances ( thyroid etc) , infections ( chills and rigors a symptoms of infections) etc.

I hope it helps. Take good care of yourself and dont forget to close the discussion please.

Regards
Khan

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