Again he paced the chamber; but an involuntary movement of awe and inquietude constantly led his eye towards the alcove. He drew near it with irresolution.
Want of resolution; want of decision in purpose; a fluctuation of mind, as in doubt, or between hope and fear; irresoluteness; indecision; vacillation
Someone who is irresolute cannot decide what to do. The worst reason to launch an attack would be a fear of seeming irresolute = indecisive. unable to decide what to do = uncertain resolute