Q: Car won't turn over. No lights come on when I turn it. Can't even lock my doorsvor push the seat up or back.

As of yesterday, I started the car up and did just fine. I did it again only to realize that when I started it up, it turned off, but turned back on just fine. Today, I turned the car on, it did give, but after using the car for a couple hours, I started the car up again and it turned off, but turned it back on and did just fine. When I got home, I tried starting the car. The lights began to flicker and go dim. I let it rest for a while, and started it again. It did fine, took it for a spin around the corner. I turned it off, played with the lights as the car was off. When I turned it back on, it started, but died on me. After that, the lights wouldn't come on, the head lights wasn't working, and didn't when hear no clicking noises whatsoever. So afterwards, I tried pushing up the seat, and it wouldnt let me. I tried locking the car and it wouldn't let me. I tried pulling down the window and it wouldn't let me. Think it's a dead battery?

My car has 140000 miles.
My car has an automatic transmission.