My left eye has started to periodically twitch on the bottom outside lid. it's subtle but noticeable to me and happens for about 4-5 seconds. ideas?

Twitching: Usually due to fatigue, stress and eye irritation. Do what you can to regulate the first two and the twitching will stop.

Myokymia: Random twitching of an eyelid, which happens in normal people, is called myokymia (an involuntary, spontaneous, quivering of a few muscle cell bundles within a muscle). Myokymia starts and stops spontaneously. In the eyelids, it can last a few minutes to a few days. It can be caused by stress, dry eyes, lack of sleep.

Other causes: In my experience, other causes of eyelid twitching(blepharospasm) include eye strain and caffeine intake. This is a benign condition and is more of a nuisance than anything else.