Aircraft has to stand reasonably still or it won't start motors. If you're rocking in the basket or not being steady enough when holding in the hand it might be too much for it.
But it's probably better that way. Unless you have your Mavic modified to give you ATTI mode and know what you're doing it would be VERY sketchy to start it there, it'll uncontrollably fly out of your hands with all the power it has as soon as the motors are started, and you'd better be on the correct side of the basket, well clear of it and with no vertical speed if you don't want rotating cutters into you and the balloon.
Without ATTI it'll also be almost impossible to safely land in the basket again, and you probably won't have enough flight time/range to go land it somewhere appropriate on the ground.
Very "advanced" move that requires full comprehension of how the thing works. Lots of people have had bad experiences on boats, this is even more difficult since there is less space, the balloon moves up/down in addition to horizontally, and damaging the much more fragile balloon due to a messup can have much more serious consequences.