Many of the symptoms of shyness are also present in cases of social anxiety disorder. These include mild physical symptoms such as blushing, sweating, or even stomach cramps, as well as negative self-talk. However, the key difference is that social anxiety disorder is a recognized mental health condition. It goes beyond shyness by affecting a person’s ability to function in social settings, causing intense levels of fear, and leading to extreme avoidance (via Verywell Mind). The disorder often leads a person to worry about experiencing anxiety itself in social situations, out of the fear that others will notice that anxiety and then cast judgment on them (via Mayo Clinic). As such, people with social anxiety tend to avoid situations where they’re the center of attention or where they might embarrass themselves.
The University of Melbourne explains that shyness is manageable, a normal component of personality, and does not cause significant levels of distress. By contrast, social anxiety disorder does cause distress to the person experiencing it. The fear and anxiety they experience also tends to be disproportionate to the actual situation, and these feelings persist for longer than six months. If you often experience extreme fear rather than just awkwardness in social settings, worry about those situations well in advance, and go to great lengths to avoid them, you may have social anxiety disorder. Though debilitating, the condition is common, and there are several proven ways to manage it.
Source: https://www.glam.com/980992/how-to-tell-when-your-shyness-may-be-something-bigger/