Not starting

My car was fine, had stopped at traffic lights then when I pulled away my car was juddering and had a lack of power, message came up saying engine system fault so I pulled over and switched the engine off. After roughly ten minutes I put the ignition on (key-less entry) and the engine system warning was away but the battery light was on, I tried to start and it started but had a strange rattle so I turned the engine off. I then tried again but this time no joy. All I got was a starter noise and the button seems like staying in until I press it off. Had to get a tow home. Now I have low battery warning please start vehicle, but I cannot start it. Any help? The battery was new in November when I got from a dealer.