If you are unsettled, you cannot concentrate on anything because you are worried. A lot of people wake up every day with a sense of being unsettled and disturbed
subject to change; "a changeable climate"; "the weather is uncertain"; "unsettled weather with rain and hail and sunshine coming one right after the other"
In an unsettled situation, there is a lot of uncertainty about what will happen. Britain's unsettled political scene also worries some investors = unstable