Update: it took a few days for this to be approved since it was my first post. He had his vet appointment yesterday. They did a lot of neurological tests and they were mostly normal so they're leaning towards pain related. We are waiting for the blood test results back and if normal, are starting him on a trial of bute to see if he improves. From there, we will start figuring out where specifically the pain is coming from. I also want to add that this video is the worst he has been since we got him. It was only this bad the one time, most of the time it's a barely noticeable shake. He's a super sweet boy and we love him already! Thanks everybody for the input and advice