For the last couple of weeks, my two-year-old son has been waking 2-3 times a night and shrieking/moaning. He settles back down to sleep when we rub his back, but it's been happening during naptime too: about 45-60 minutes after falling asleep, he wakes up shrieking and covered in sweat. It's gotten to the point where he's scared to go to sleep. He used to go right to bed at night, but now he fights it, crying, and at naptime, he tries as hard as he can to keep his eyes open, even though he's clearly exhausted. Has anyone experienced this? How long does it last, and is there anything we can do for him? Thank you!