A desire arises with the memory of a pleasant experience and past impressions.
A desire might arise through listening.
A desire can be triggered through the association of certain people and a place.
Someone else's need or desire may manifest in you as your own desire, e.g. when someone is hungry, you get a desire to feed them or someone wants to talk to you and you get a desire to talk to them.
The destiny or a happening in which you have a part to play may trigger a desire of which you have no idea. For example, a gentleman in Quebec, Canada kept making roads and working on a farm for 30 years, not knowing for what -- for it was destined to become our Canadian Ashram.