Sleep is apart of the natural order and since he killed the king, he disturbers the natural order. Without sleep he has no rest.
Perhaps because he's disrupted this, and is rambling about it, he is representing guilt also.
it simply means, that when he killed the king, he also killed sleep. Macbeth now wont be able to sleep because of the guilt of killing the king
"Sleep no more, Macbeth doth murder sleep."
Macbeth murders sleep
In Macbeth, insomnia is a symbol for guilt. "Macbeth hath murdered sleep, the innocent sleep, sleep that knits up the ravel'd sleeve of care . . ."
Lady Macbeth tells Macbeth to hide his emotions and actions.
Of course, Lady Macbeth has her famous sleepwalking scene in which she not only walks but talks in her sleep. It is clear that she is disturbed and unable to sleep properly. Indeed it is a recurring theme that the Macbeths have, by committing their crime, deprived themselves of a good night's sleep. A voice tells Macbeth as he murders Duncan, "Sleep no more, Macbeth hath murdered sleep." Later he expresses envy for Duncan because, "after life's fitful fever he sleeps well", and still later Lady Macbeth tells him, "you lack the season of all natures, sleep." which suggests that Macbeth has not been sleeping well.
After killing Duncan, Macbeth could not sleep. He feels the guilt and is terrified
That Macbetbh had murdered sleep.
Duncan
she tells him to go bleep and blop
Lady Macbeth's disturbed sleep represents her guilty conscience and inner turmoil over the crimes she and Macbeth have committed. Her sleepwalking and hallucinations reveal the psychological weight of their actions on her mind and spirit.
In Act 2 of Macbeth, King Duncan is murdered by Macbeth in his sleep. Lady Macbeth also kills the two sleeping guards to frame them for the murder.