I saw the International Space Station when the space shuttle was hooked up with it a month or so ago. I found a schedule which showed exactly when it was expected to travel over where I live and what direction it would be traveling so I am certain that is what it was.
When I saw it, it traveled from the northwest towards the southeast. It wasn't visible until it was about five degrees above the horizon. Then it brightened quickly and it continued to brighten until it was really bright when it was straight overhead. It got less bright as it traveled farther along and disappeared when it got to within five degrees or so from the horizon.
I didn't time it but would say that it took about five minutes to travel clear across the sky. I didn't notice that it moved in an erratic fashion. It moved quite steadily.
I will see if I can find that site that gave the ISS's schedule so we can know for sure, but I would think it wasn't what you saw. Could be wrong though. ;-)
I'm still trying to wade through all that talk about azimuths and such to see if I can figure out anything. I am a very amateur astronomer ..... don't understand all the technical jargon ....... :-)