What could cause a vibrating sensation in the penis?

Rumbly: Doubt it's the penis. Likely bowel.anxiety could also cause this. If persists go see your doc :)

Most common cause: The most common cruse is a vibrator in proximity. Also.look for purring cats. If your search comes up negative you need to see either a neurologist or a urologist. Be be sure to bring your meds. You will likely need to get a blood test for causes of neuropathy.

Phantom cell phone: strong evidence for phantom vibration sensation in individuals who routinely keep cell phone in front pocket. sensation can often re-occur in the absence of phone