This study investigated the influence of imagery-based suggestions on motor behavior. Furthermore, it tested whether this modulation of motor response influenced the phenomenological experience of wakefulness and alertness. Without prior hypnotic induction, participants listened to 90-s scripts consisting of imagery-based suggestions. In one script, they imagined two dictionaries being progressively placed on their left hand (i.e., heavy objects). In another script, using the same procedure, they imagined two paper sheets (i.e., light objects). Throughout each script, they stretched their left arm with the instruction not to move. As expected, the results showed a greater arm lowering and a greater perceived effort in the “heavy” script than in the “light” script. This suggests that imagining physical interactions with objects can reactivate old sensorimotor traces embedded in the memory, related to past sensorimotor interactions with these same objects. Furthermore, we assessed participants’ perceived variation in the phenomenological experience of wakefulness and alertness in comparison to a situation in which no script would be presented. Participants perceived a greater variation in the phenomenological experience of wakefulness and alertness in the “heavy” script than in the “light” script. Regarding the cold control theory, these results suggest that the metacognition about motor intention and agency would be more disrupted when the script induced greater “involuntary” arm lowering (i.e., “heavy” script). This would therefore influence the phenomenological experience of wakefulness and alertness.