I would practice allowing yourself to be uncomfortable in places where you are physically with other people.
simple examples are like when you are in line for something and waiting right next to someone in line for the same thing. chat them up, you have a lot in common right then. it's uncomfortable, but you have nothing to lose once you are no longer queued
or on your street, when you see someone else getting in or out of there car for the 20 seconds it takes. say something awkward to them. it's uncomfortable, but the next time won't be as much
start simple! there are opportunities to practice this in little ways every day!