Cheeks and lips have been randomly trembling or twitching. what could cause this?

Lip Twitch: Lip/ cheek fasiculations have many possible causes (i.e., too much caffeine, certain meds, low potasium, hypoparathyroidism, start of Bell's palsy, tic's etc). On the otherhand there is a good chance that there is absolutely nothing wrong & you just have an occassional twich. REF: https://www.healthline.com/health/lip-twitching

Twitching: True that stimulants and the like can be a cause for twitching. Hormonal causes such as thyroid excess possible too. One common correctable problem is electrolytes. Often twitching is associated with an imbalance between your calcium and magnesium. Magnesium low in diet especially in north America. Mag glycinate can often help.