Oh great, Starlink "cluster flares" are a thing now: https://skyandtelescope.org/astronomy-news/freaky-starlink-cluster-flares-glimmer-in-the-dead-of-night-comet-lemmon-bright/
(watch the video that's the second photo inside the article text)
So yeah, if you see a bright flash in the night sky for just a moment, you're not imagining it, it's probably Starlink. Or maybe space junk (up to 80,000 glints per hour now): https://www.universetoday.com/163985/satellites-make-up-to-80000-flashing-glints-per-hour-its-a-big-problem-for-astronomers/