What a great question! Are these song lyrics? If so, they are probably open to interpretation, but I will give you my best guess! "I hear echoes in my head" probably refers to a recurring memory or sound. For example, if there is a catchy song that I can't get out of my head, I might say that "I hear echoes [of the song] in my head." It could have a similar meaning if something really terrible happened that I can't forget. For example, if I saw my best friend killed in a car accident, the sights and sounds would be unforgettable to me, so the accident would "echo in my head." "Sheisty" is a slang word for acting suspicious. "Shiftin" is slang for something that is changing regularly and/or being suspicious. If you are interested in learning slang or discussing English lyrics let me know!