It's very possible. Introversion is not the same as shyness. All introversion means (regarding social skills) is that someone needs time to recharge and be alone after a certain amount of interaction. They feel overwhelmed by too much interaction too soon, but it doesn't mean they're afraid of people or that they have bad social skills. I see introversion as eating too much cake, lol. You love cake, you're not afraid to eat cake, and you have no problems approaching it, but after so much, you need to back off and restore your homeostasis.
A shy extrovert desires to be around people and gets energy when constantly interacting with others (as opposed to getting drained and needing to retreat for a little while), yet is afraid to initiate that interaction.