What Causes Tiredness With Family History Of Heart Disease?

I m 66 years old, family history of heart disease. I have been sleeping between 10 up to 13 hours a day. I wake up tired. I ve had numerous blood tests and nothing significant shows. I was always a very high energy woman and in the past two years I cannot stop sleeping long hours. I m not depressed but was prescribed Zoloft for many years when I was depressed in the past and still on it, 50 mg/day. I do toss and turn, do not drink coffee after breakfast, no caffeinated beverage either. Is there a possibility this is a neurological issue? Thank you in advance.