They seem to do this, in my experience, whenever they are excited. As a footnote, the position that most parrots find the most comfortable when excited seems to be hanging upside-down. Presumably because this is the most stable, pendulum-like configuration. I have also noticed it is also the default position for broadcasting "look at me, I'm strong and beautiful!" It sometimes has seemed to me that the looping is caused by cycling through that "look at me" position. However all of that, it must be admitted, is amateur bird-whisperer speculation. My CAG Sophie used to do loops like that whenever I entered the room, or called to him (yes, him as it later turned out - I named him long before there was PCR sex testing) from the kitchen. He eventually got it down to up to the the roof, then back to the main branch - then repeat. That was for everyday use. But when he was really excited he sometimes did a whole circuit across the roof. But I'm thinking the precise details may depend not only the bird, but the geometry of the cage. If your bird eventually gets onto your arm after a few loops I'd chalk it up to pure excitement and/or showing off for you. Otherwise maybe look for what it is that is getting her going. If you meant "grab" literally maybe she has mixed emotions about that. Excitement can sometimes be a double edged sword, as most parrot owners figure out pretty fast!
