I'm not sure if I agree with Hamlet being a "coward" - I think he just wants to make sure he does everything right. In the right order, to the right person - he's very concerned with getting things right.
I suppose it is possible that he courts annihilation. After all, wasn't he pondering at one time whether it's better "to be or not to be"?
No. Quite the contrary, I think, he plays much the coward throughout the play. He is constantly over analyzing what he must do, murder the king to avenge his father's death. He is not the typical hero he is not fearless. I imagine that someone who "courts annihilation" is someone who is fearless who acts now and thinks later not caring if the act might end in death. I don't think that Hamlet wants to be annihilated and I don't think he truly wants his mission, but he is willing, grudgingly so, to do what he must to preserve his father's honor.