Music snow globe started to play on its own?

Ok so it's 1:44 am EST where I am im about to go to sleep suddenly my snow globe music box started to play as if someone turned the key im a bit freaked out right now. It has done this in the past the key is in there could it be from movement on the bookshelf its on or the cold weather
It played for at least one minute maybe more.

You are on the right track. The spring just drives the music box till the force of the spring can no longer overcome the forces of friction caused by the mechanical system. It could stop prematurely due to a piece of fluff, grit or hair, even an ant, especially combined with sludge forming in the oil it is lubricated with. If well worn, parts can become misaligned enough to stop it, even near the start when the spring is wound up tightly.. Most of them have a stop switch too, a small lever, that could move again.

What could start it going is:
a bump in the right direction, maybe the building settling in cold weather.
a change in temperature, especially upwards (a heater in the room or just your own body).
the stop lever moving due to temperature cycling.
the gears moving due to temperature cycling.

I have seen nuts undo themselves with temperature cycling. It is a sort of ratchet action. This sort of action could realign parts, release a stuck part, release a stop lever or relieve a stuck spring, especially combined with a bump.