I have a very similar problem causing severe sleep-onset insomnia. I went to a sleep disorder center, a really good one, and they couldn't figure it out except to confirm that I was waking up during sleep-onset over and over again according to the EEG without apnea or myoclonus, although to confuse matters, I have some daytime myoclonus, but that doesn't accompany this from what I can tell.

So I've been stuck on ambien for 15 years. I'd love to stop taking ambien, but the problem lasted for so long and was so intense that I stopped really sleeping. It feels like someone shouted "Boo!" in my ear, which causes me to wake up, and then it keeps happening over and over again. Unlike a hypnic jerk, I did not feel like I was falling and did not physically jerk, so that was ruled out. I've not seen this described in any sleep books, so I don't know what it is.

Strange. You're the first person I've heard say this. I hope they figure it out. If you find out, will you post here? I've been trying to find this out for 15 years now. Luckily, medication does help me, but only ambien; I tried dozens of other sleep medications without luck.