"unstable nature" is correct and usable in written English.
You can use it to describe a situation or person that is unpredictable and constantly changing. For example, "Sam's unstable nature made it difficult to keep up with his shifting needs."
To term Pakistan cricket indomitable is not to deny its essentially unstable nature.
It also gave him an early appreciation of the unstable nature of all things.
The structure of the text, a mosaic of fragments, mirrors the unstable nature of memory.
Giggs, who is Louis van Gaal's No2 at United, stated that his involvement in Salford is security against the unstable nature of football.
Peter O'Toole takes the lead, and while the intensity of his gaze hints at the unstable nature of Lawrence, it's a distant gaze.
Immediately south of the convergence zone, rainfall is heavy because of the unstable nature of maritime tropical air over a heated land surface.
"Who if not I, then, is Amphitryon?" As that line suggests, Banville is back to one of the persistent preoccupations of his recent fiction: the elusive and unstable nature of identity.
And he set about turning it on its head, using its chaos, its unformed and unstable nature, its violence, and making a myth out of that, something stable and everlasting, raising it to the very highest level of literary achievement.
The bits of newspaper symbolised the conflicting fictions upon which nations are built and the encaustic, an unstable material, was perceived by critics to be a metaphor for the unstable nature of identity.
Thanks to the unstable nature of the dyes, the colour green was considered deceptive, and became associated with games of chance – which is why card tables and snooker tables are covered with green baize today.
The unstable nature of the soil and rock in the area of Gaillard Cut made it one of the most difficult and challenging sections of the entire canal project.
