I seem to get them more often when I'm concerned about waking up or focused on something related to waking up. For instance, there was a time in my life many years ago when I would frequently take naps during the day (to catch up on sleep which I was never able to have) but needed to not sleep too late. I was frequently concerned about this; I ended up having FAs on a regular basis (as well as some LDs, as a nice side effect ).

When I've taken to record notes about dreams on each awakening, I also often have FAs, usually centered around grabbing the recorder and trying to note the dream, only to wake up and have to do it over (if I manage to still remember it). Annoyingly, RCs seem not to show up in many of these even though my habit has been to RC on every awakening for nearly a year now.