Sounds like a happy Corgi "Arroooooo" to me also. My late Corgi pal Tinsel had a lovely "aroooo" that she would offer as a greeting every morning. Very endearing trait of our furry pals.
Luna has started making this weird wookie "arooo" sound right after she wakes up. I think it's such a cute sound for her to make and I hope it continues.
LOL it makes me laugh to discover these things I think are unique and everyone's doing it! I heard arrooo for the first time when I was fostering a corgi - my Sophie then picked it up. She does it just before getting her breakfast. Never at dinner, only breakfast for some reason. I love MyCorgi!!
Any time either of our corgis makes a different sound we encourage it. Just got to love those sounds and this one is in top game for making sounds. You are very lucky.
Oh my goodness! Kirby just started doing this in the past couple weeks. It totally freaked me out at first. Ha ha... She just goes right back to sleep like nothing happened. Lol