[2] Motor disorders are malfunctions of the nervous system that cause involuntary or uncontrollable movements or actions of the body.
[4] Symptoms of motor disorders include tremors, jerks, twitches, spasms, contractions, or gait problems.
Twitches or jerks of body parts may occur due to a startling sound or unexpected, sudden pain.
[5] The way humans move requires many parts of the brain to work together to perform a complex process.
There are constant signals being sent to and from the brain and the muscles that regulate the details of the movement such as speed and direction, so when a certain part of the brain malfunctions, the signals can be incorrect or uncontrollable causing involuntary or uncontrollable actions or movements.