Thank you, scampster. Yes, my doc looked at other symptoms as well, and he thinks that sleep apnea is unlikely.
That said, I'm really not trying to convince anyone that I have a condition I haven't been diagnosed with, and it might indeed be that I'm simply not getting quality sleep for whatever reason. I was just wondering if anyone had experience dealing with uncontrollable sleep attacks (particularly in the workplace.) For me this is different than just being tired because it happens very suddenly - one moment I feel just fine (i.e. not tired), and the next I'm falling asleep and can't fight it.
I had something like that going on at one point, but it was blood sugar related. I didn't connect the dots for some reason-- but I'd get these crashes where I knew I had about a minute before I was going to be unconscious.