What satellite is this?
It sounds like a tumbling satellite and by your description of the different locations in the sky during the second pass, it sounds like you saw the same one over the course of two orbits.  Maybe not, though, because it'd (most likely) be 90 mins from one orbit to the next and conditions would have to be just right for the geometry of the Earth/Sun/Satellite angle to make it visible for two orbits so brightly. But not impossible!  The Starlink satellites don't vary in brightness that way, so I can safely say it wasn't a Starlink. Tumbling sats can be wild to see, some are spinning very fast and flicker quickly (a couple of times a second) while others are doing a much slower tumble.  Sadly, there is a lot of space junk up there launched without a plan to decommission it (bring it down over the Pacific to burn up harmlessly).