Are there any kind of restrictions on Pakistani Nationals to enter in Goa, India, for any reason?
If so, what are the restrictions?
Not as far as I can tell. As I'm sure you're aware, the visa application process for Pakistani nationals visiting India is lengthy and painful, but the High Commission of India in Islamabad's site only notes that "Prohibited/Restricted/Cantonment Areas" are off-limits. RAP/PAPs are listed here, and while eg. much of the north-east and Kashmir are on the list, Goa is not. Cantonments refers to the military quarters scattered around India's cities and a tourist wouldn't have business there anyway.