I Am A Male In My 50's. My Head My

I am a male in my 50's. My head my head feels like it is shaking inside. I have had an Mir and a cat scan and nothing showed. I have had this for 3 years. I have been prescribed numerous drugs but nothing is working. Right now it is on a cycle of good day where the shaking is minimal or non existent and bad day where I have the sensation of my brain shaking all day. When I am horizontal it is not as noticeable. Any insight would be appreciated. Thank you.