Hallo Carla and welcome.
Xanth is correct, what you are experiencing is indeed sleep paralysis (SP). SP is really nothing to fear, it is a common occurrence that prevents a person from getting up and physically acting out their dreams.
In addition you may also be experiencing a phenomena known as "Dwellar on the Threshold". I won't go into detail here but do a search (Google) and you will get a lot of info about this.
Regards

Grey