Because the person sending these messages to her subconscious can't always predict her sleep schedule, and can tell when she's fully awake or asleep but not when she's making the transition, she occasionally receives one just as she's waking up. She's not aware that she's receiving anything, as the information bypasses her conscious mind, but she gets a feeling like a painless electric shock, and hears a sound like a radio makes if you touch its antenna, which is enough to wake her up fully and leaves her feeling startled.
After determining that this is not caused by too much caffeine (she stops drinking coffee) or radio waves being picked up by her fillings (she doesn't have any), she decides to go to a doctor to see if there's something wrong with her.
My question is, what might her doctor suspect was going on here? Is there anything physical that might cause this type of symptom? She's conscious of it no more than once a month, and has no way of predicting when it will occur, and I'm not sure if it would leave any evidence other than an elevated heartrate. Would the doctor need to monitor her while she was sleeping, or is there something else he could test for in a different way? It's okay if the tests are negative or inconclusive, because I need them to move on to psychological problems afterwards.
Speaking of which, what might a psychiatrist suspect?
I googled "sleep disorders", but I don't have enough medical knowledge to narrow it down any more than that.
ETA: I neglected to mention that my character, by the time she decides to trouble her doctor about this, is developing insomnia due to being entirely freaked out by her morning jolts, which makes her sleeping patterns less predictable and thus ups the frequency of the mistimed messages. So at that point it's happening on something like a weekly basis, as opposed to the first eleven spread out over a year.
Also, while I would certainly appreciate more input, I think her doctor is going to suggest exploding head syndrome. Because who wouldn't want to devote a chapter or two to that?