He may be just trying to get some attention. My RB Sunny would howl late at night or in the early morning hours because he wanted to play with some one. My other cats just wanted to sleep so they would ignore him. I would even find mice all lined up outside of my bedroom door. The poor boy had so much energy being half Aby and no one would play with him. Hopefully whatever is causing this isn't anything more serious. I've also heard that sometimes older cats will do this because they feel lost in their homes. They get a form of Alzheimers disease.