What are the reasons for Hamlet's hesitation to kill Claudius in Hamlet?

Hamlet hesitates to kill Claudius because he wants to be
certain that Claudius is guilty.

Hamlet reenacts a
murderous scene, searching for a visible sign of guilt from
Claudius.

Hamlet cautiously searches for a
definitive, visible sign of guilt.  He wants to be absolutely certain
of Claudius' guilt.

This is a tragic flaw for Hamlet. 
His insistence upon finding visible guilt from Claudius delays his action of killing
Claudius, thus delaying the avenging of his father's
death.

Hamlet's procrastination is well reasoned in that he
desires to know the truth in reference to his father's
murderer.

Nonetheless, Hamlet's procrastination allows
Claudius time to suspect Hamlet's actions of avenging his father's
death.

Claudius has Hamlet banished in a plot to have
Hamlet killed.

Although Hamlet's hesitation to kill
Claudius is an honorable quality, it is a tragic flaw that costs Hamlet his life,
ultimately.