My son is almost three and I’m curious is this normal behavior for a almost three year old?

Ok, so for a while now maybe over a year now.

When we put on a movie and it starts no matter what movie it is.. whether he knows it or not. He runs and hides behind a wall, couch, pillow, or blanket. Or grabs our hands or arm to block the movie. After it starts after the 20th century sound or the lamp jumping on the letters. He runs and smiles and laughs.. he’s like excited. Jumps for joy even.. is this normal behavior Or? Should I be worried. I don’t know what started this behavior it was just randomly started one day and he’s been doing it since.. if we skip that part of the beginning he doesn’t do anything.. he still excited as he should be does the exact same thing just besides the hiding .. he smiles and laughs now if I join in on the 20th century song & he just looks and smiles and tries to join in sometimes now. Is this just a normal thing?