What Would Cause Hand/arm Tremors? Started About Five Years Ago

what would cause hand/arm tremors? started about five years ago but getting worse, more often, lasting longer and shaking more noticeable. most obvious in my hand. I also shuffle when I walk. I have a long history of asthma, and possible head trauma as young person. I also have a hearing loss on one side that is very pronounced. I have had several Head MRIs over the years, most recent this year. Nothing appears abnormal. why is this happening? what should my doctor be looking at?