Our 8 month old daughter started presenting symptoms of what has been diagnosed as benign myoclonic jerks of infancy
. About 5 or so times a day she would have a cluster of upper body jerks (arms, torso and head) which would resemble a startle response. Each one would last about 2 seconds and would be about 20 seconds apart. A cluster can last anywhere from 2 mins up to half an hour. She can't be distracted while doing them and tends to be sleepy after them.