This happened to my mom all the time when my brother, sister and I were at school.

My mom would drop us off at school and she would come home and sleep, but when she's sleeping, she would feel someone tapping on her arms, or legs yelling "MOM, MOM, MOM!!!" She would wake up and no one would be there and she would fall asleep again and it would happen again. She said that she thought it was us cause that's what we would do sometimes, but then she would remember that she's home alone.