Anxiety that seems to come from nowhere is more common than many people realise. Sometimes there is an underlying trigger you have not consciously noticed, such as accumulated stress, poor sleep, or worries running in the background. In generalised anxiety disorder, persistent worry and a sense of unease are present much of the time without a single clear cause.
Physical factors can also produce anxious feelings, including too much caffeine, low blood sugar, hormonal changes, certain medicines, and occasionally thyroid or heart conditions. This is why unexplained anxiety, especially if new or accompanied by physical symptoms, is worth mentioning to a doctor who can check for contributing causes.
For occasional episodes, grounding techniques, slow breathing, physical activity, and reducing caffeine can help. If anxious feelings occur most days, feel hard to control, or interfere with your life, see a doctor or mental health professional. Effective treatments, including talking therapy, are available, and identifying any underlying cause is the first step.