Parkinson’s disease is a progressive disease of the nervous system. It is estimated that 4 to 6 million people around the world suffer from the condition. Parkinson’s disease becomes more common with increasing age, though there are those diagnosed with early-onset Parkinson’s disease. Symptoms of the disease usually first appear in people over the age of 50, although as noted above, younger people can also develop the disease. There is no evidence that Parkinson’s disease is hereditary, although in around 5% of cases there is another family member affected.

Signs and symptoms:

 Three common PD symptoms that gradually develop are:

• Slowness of movement (bradykinesia). For example, it may become more of an effort to walk or to get up out of a chair. 
• Stiffness of muscles (rigidity) and muscles may feel more tense. Also, your arms do not tend to swing as much when you walk.
• Shaking (tremor) is common, but does not always occur. It typically affects the fingers, thumbs, hands and arms but can affect other parts of the body. It is most noticeable when you are resting. It may become worse when you are anxious or emotional. 

Some other symptoms may develop due to problems with the way affected brain cells and nerves control the muscles. These include:

• Fewer facial expressions such as smiling or frowning. Reduced blinking.
• Difficulty with fine movements such as tying shoe laces or buttoning shirts.
• Difficulty with writing (handwriting tends to become smaller).
• Difficulty with balance and posture and an increased tendency to fall.
• Speech may become slow and monotonous.
• Swallowing may become troublesome and saliva may pool in the mouth.
• Tiredness and aches and pains.

When to see a doctor?

See your doctor if you have any of the symptoms associated with Parkinson's disease — not only to diagnose your condition but also to rule out other causes for your symptoms.

https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-disease-Information-Page

https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/symptoms-causes/syc-20376055