He was standing near to the TV. (distance is short.)
"Step back. Dont stand close to the TV."
Does it sound natural and grammatically correct?
Step back. Dont stand close to the TV.
It's an imperative sentence. And this is a completely grammatical sentence.
The verb - stand - can license a Preposition Phrase (PP) as a complement, and that can express the location/position of the subject. Here the PP is close to the TV, and the head Preposition is close; within this PP structure the head preposition takes another PP - to the TV - as complement.
In the nested PP - to the TV - the head preposition is to, and it takes a Noun Phrase (NP) - the TV - as complement.
N.B - The to in the PP close to something is a Preposition, not the infinitive marker, and that's why it's incorrect to use the base form of verb after that to.
They are very close to winning the game. [CORRECT]
They are very close to win the game. [INCORRECT]
Don't stand close to the TV is a natural sentence. You can even say, "Don't stand too close to the TV" if the distance is really short. If a person is sitting close to the TV you can change stand to sit.