M.F.
She may be on the verge of a cold. Maybe the temp of the room is too hot/cold. Or possibly it can be food related (nothing too close to bed time, sugary, or heavy to digest). If she does wake up the best thing you can do is keep all movement to a minimum. Changing diapers and drinking cool water actually helps wake them up. Stick to very few words and quiet soothing (rubbing back, shh etc) as soon as she wakes. the longer she is awake the more awakened she will become. good luck