fickle
adjective
uk/ˈfɪkl/ uslikely to change suddenly and without warning:
Do Americans know how to invest in fickle markets?
The art market is as fickle and hard to predict as any other.
likely to change your opinion or your feelings suddenly and without a good reason:
Brand loyalty is hard to get from the notoriously fickle internet community.
fickleness
noun [ U ]
Many e-businesses are complaining about the fickleness of investors.