I am not the most knowledgeable when it comes to bikes so please bear with me. I have a Claud Butler and after fixing a puncture I decided to ride it. As I was riding, I could hear a sort of rattling whilst in the low gears, but then when I went up in gears, I noticed that the sound continued but also it felt like the chain was slipping. After inspecting it later, I believe it has something to do with the rear derailleur, as every now and then it would spring forward a little and then return to just the rattling sound.
What could be causing this problem, and what can be done to fix it?