Unless you have a deal that needs to be negotiated, or you have a body of paid work that justifies a studio or showrunner considering you for a writing gig, you simply don't need one yet and it shouldn't be the focus of your writing. Write three scripts a year. Enter quality contests. Get better. Get read. Pitch your stuff to anyone listen. Too many writers focused on representation are putting the cart before the horse. If you think "but if I had an agent they would get my stuff read and then there would be a deal," then you're going to be increasingly frustrated and risk burn out.