I've got bad anxiety but when i think i'm relaxed i get an attack out of the blue why is this and what are the sudden symptoms?

Normal for panic: Panic often hits a person in their quiet moments. If you are worrying or thinking about anything that has to do with loss, separation, death, or abandonment you are more likely to panic because of dysfunction of the locus coeruleus in your brainstem. These thoughts may be conscious, preconscious, or unconscious. It is thought that the bustle of daytime keeps these thoughts suppressed, and then when things are quiet, these concerns surface and trigger panic.

Bad Anxiety: It seems you are not completely relaxed possibly due to many stresses in your life. Please see a psychiatrist. You will benefit from psychotherapy and medication.

Panic attack: Sudden intense anxiety or apprehension accompanied by sense of impending doom and other hyperarousal symptoms, either due to medical causes or part of panic disorder. Review with your doc.