Trouble Locking/Unlocking and Starting Car

I did a brief search on the forums for a similar problem, but I didn't find one, so i apologize if this is a repost.

Over the past few days, my Prius (2001 model) has been acting a little strange. There have been several times I go out to unlock the car and it won't unlock using the remote. You can hear the car trying to turn the locks and the dome light flickers, but it just wont do it. The first few times this happened, eventually it unlocked and I got into the car, put my foot on the brake, put the key in the ignition, and tried to start it. The dash lights up at this point, then shuts down and the car won't start for a few minutes. I just have to wait it out and then try again.

As time goes on, it's happening more frequently. For example, just last night I went out to my car and nothing happened at all when I tried to unlock it. You couldn't hear the locks turning or anything, so I sat there and tried a few times thinking I did something wrong, but I eventually just had to manually unlock it. After I did that, I turned the ignition to 'On' before I tried to start the car, and the dash lit up like usual, but then it started flickering and you could hear a really strange turning noise in the car - then it shut off completely. Again, I just waited it out for a few and tried again and it worked. Once the car is started, it runs fine, but I don't know what's going on. Any ideas would be greatly appreciated.

 

I had the same thought, especially since it is the original. Think that will do the trick?

 

Thanks to all of you . I replaced my 12V battery and everything is back to perfect! Thanks again everyone.