S.R.
Could be "night terrors" (I know, they happen during the day). These are different from nightmares, in that they usually happy early in the nap or night, within 30 minutes to 2 hours after falling asleep. It's a disruption in the sleep cycle where you wake up scared, even if you haven't had a nightmare (usually we don't dream until a couple hours into sleep, so this is pre-dreaming). Some people are just prone to them, and they are especially common in young kids (but I STILL get them as an adult sometimes). Being overheated or overtired can make them more likely.