Talk to Neuro Physician on Shaken Baby Syndrome

My baby is 2 months old and she wasn't sleeping so her dado brought her close to her face and shook her a very little that why aren't you sleeping. It wasn't vigorous but i'm afraid could it result in a shaken baby syndrome? I just read about it online and too afraid. It's been 4 weeks to it and baby is acting totally normal. She is taking proper feed, smiling, playing and all. What are the symptoms of shaken baby syndrome? Do the symptoms increase overtime or not? What should be the severity of shake?