My daughter went through the same thing. She would have a horrible dream and wake up screaming with all her might and scare me half to death. We have no clue why it started, but she was about 2 1/2. She never remembered any of them, except one, which must have been so vivid and real to her that she couldn't forget it. And to this day she will tell you there was an "owl" in her bedroom and that it reached out and grabbed her leg when she was running away to come get us. She doesn't like to not have curtains...cause she can look out at night and "Owl's" can look in. She seems to have a slight fear of "owl's". I'm not sure what to do with that but she is 8 1/2 now and she still swears there was an "owl" in her room, she no long has the night terrors, but once in awhile she does have a really bad dream that sends her flying down the stairs or we hear her cry out.
My son never went through this. He is currently 5. But he does do a whole lot of talking/yelling in his sleep!
All I can say is if it's anything like what my daughter went through it will last a few months (that feel like a life time) and then be done. Comes and goes just as fast.
Hang in there!
~T~