I am not sure from your question whether your baby son appears to be unusually stiff when compared to other babies of his age. Many babies may look a bit 'startled' and stretch when they wake up and this is entirely normal.
If his arms and legs appear unusually stiff and also if he seems to jerk his arms and legs at times or arch his back then he should be seen by his paediatrician. This is just to make certain that he is completely healthy.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.