I only get them once or twice a year; there’s always a very tiny feeling of headache that only lasts a few minutes, but the jagged lightning-bolt thingies on the periphery of vision last about 20 minutes. Almost always set off by seeing some kind of flashy-light business.
That describes mine pretty much exactly except I don’t know what causes them. Like you, maybe a couple of times a year.
Probably connected with stress, mental or physical but not certain.