What are the milder, more subtle symptoms to Parkinson's disease?

Many. Mild poverty of movements, falls, writing in small letters (micrographia) inability to change positions especially in bed, diminution of the sense of smell, constipation or urinary problems etc.
Further Detail. Before overt physical symptoms begin, one can experience pre-motor parkinson's issues: the most reliably reported 4 are chronic constipation, chronic depression, anosmia (part or complete loss of smell--which also effects taste appreciation) & rbd. Rbd stands for rem behavior disorder. Rem  (dreaming stage sleep) can be accompanied by acting-out of dreams: talking, kicking, punching, running, etc.