For me, the early warning signs of PD were balance which caused me to swerve when I walked.
This was especially true in the late afternoon when I was fatigued. There was also "freezing" in doorways, which was frustrating because I just didn't know why I couldn't move forward. A soft voice was also a problem and noticeable to other people.

When I began taking Carbidopa/Levodopa many of these symptoms lessened or were no longer a problem.