Crazy Transmission

Hello, what this fault of my Shadow car can be, I turn it down and walk more or less 1 km. And then he does not want to advance, I turn it off, and when he turns it again, another section progresses, and so he works all the time, I am a macho hobist, and if it is in my hands, I will fix it, I will start by removing the silk or filter, and I have such going, greetings.