1999 honda accord

I have a 1999 honda accord ex V6 coupe. I very rarely drive it and it has been sitting in my driveway for about 10 months. I bought a brand new battery for it about a year and a half ago. I'm trying to sell the car and had to jumpstart the car because I thought that the battery was dead and that's why it wouldn't start. The car started when it was jumped, but while it was idleing the rpm meter would drop down to 2 and then kick back up again like there was a surge of power and it kept doing this over and over again until I turned it off. It doesn't seem like this is the battery, but when I turn the car off it won't start again. I know absolutlely nothing about cars, and I am trying to sell this one since I never use it. Please help!

Jamaal, San Diego CA