I was riding the mower and there was something in the yard so I got up so the mower shut off. When I went to start the mower back up it won't turn on. All I hear is a small click when I turn the key. I bought the mower used about a month ago and this is the first time I've had any trouble starting it up. Any help would be greatly appreciated. I am far from an expert when it comes to mower engines.