It doesn't have to be "be relaxed" instead of just "relax?"
Native speaker’s answer
Rebecca
No, it doesn't! In "be relaxed," "relaxed" is an adjective. But here, "relax" is a verb, so "be" isn't necessary. Ex: I'm going to relax at home and take a bath. Ex: She was so relaxed during the test that she started humming to herself.