I have learned the following sentence is grammatically correct because it is possible to omit the nominative relative pronoun in a sentence like "there is ...". I'm not sure if it is natural or not in real, however. I would like to ask three questions about it.
There's somebody wants to see you.
Q1. Is the sentence natural? Why?
Q2. Does the inclusion of the relative "who" make a difference in nuance? If so, what is the difference?
Q3. Is it possible to use "there is" instead of the contraction form, "there's" in the sentence? Why?