My daughter does the same thing. Night terrors are hereditory & after getting used to my husband waking up screaming I knew it was the same thing in her.
He probably can't remember the dream, but usually they are of being chased or falling.
I've found that heat and what she eats during the day make a difference, Also, when kids wake up crying it could be because they're tired, so ensure regular rest times through the day.
It's not that big a deal unless it's happening all the time and real disrupting your sleep.