Well, according to the dictionary, unwind (RELAX) (unwound, unwound) /Vn"waInd/ verb [I] (ALSO wind down) means to relax and allow your mind to be free from anxiety after a period of work or some other activity that has made you anxious: e.g. A glass of wine in the evening helps me to unwind after work. Also, switch off means to stop giving your attention to someone or something: e.g. If he gets bored, he just switches off and looks out the window. As you can see, both verbs sound natural in the context you provided.