wakeful

carefully observant or attentive; on the lookout for possible danger

• “a policy of open-eyed awareness”
• “the vigilant eye of the town watch”
• “there was a watchful dignity in the room”
• “a watchful parent with a toddler in tow”

(of sleep) easily disturbed

• “in a light doze”
• “a light sleeper”
• “a restless wakeful night”