When you are excited sympathetic system will be active which gives you adrenaline high, also when you are anxious the same system is active but this time it causes anxiety - the emotion is different, perception is different. When you get abnormal high on excitement (shivering) and excess anxiety in relation to stimuli then its pathological/considered as a problem. So please consult a psychiatrist for evaluation

Shivering when excited or anxious is a normal response due to heightened excitability as there is increased amount of neuroendocrine hormones in such situation which can cause this. For these symptoms if problematic one must see a mental health professional who can explain the reason behind all this and can manage the symptoms pharmacologically as well as non pharmacologically.