If you have social anxiety, then approaching someone is a matter of practice. You can't approach someone if you continue to avoid doing so...so practice! But you don't start out by going all in and make an initial face-to-face encounter. You have to use baby-steps...start small by just imagining, in your mind, you approaching someone. This may give you some anxiety, so you can use some relaxation techniques, like diaphragmatic breathing and progressive muscle relaxation, to calm you down. So continue to imagine approaching someone, and continue to use some relaxation techniques to calm yourself down.
When you are successful at calming yourself down, then you can go to the next level of practice, where you might just get out of your social isolation and just be with other people. You don't have to talk to them...just be in the crowd. This may cause even more anxiety, so if relaxation techniques are not enough to calm you down, then you may need assistance, such as taking a natural anxiety supplement such as KalmPro.
When you are able to practice enough times and you are able to calm yourself down successfully after practicing, then you can go to the next level, which is to actually approach someone. So just start with a simple greeting...a 'hello' will suffice. Practice this with a few people initially, then gradually increase your number of people you say hello to each time. Eventually, with enough practice and using relaxation techniques (and maybe using KalmPro), then you can successfully approach someone without being interrupted by social anxiety.