Having a tendency to change one's mind frequently

Unreliable in nature

अविश्वसनीय स्वभाव

English Usage: His fickle-minded nature made it hard for his friends to trust him.

Hindi Usage: उसकी अविश्वसनीय स्वभाव के कारण उसके दोस्तों को उस पर विश्वास करना मुश्किल हो गया।