My Iphone Won’t Stop Vibrating When Charging?

I think there’s something wrong with my charger. The cable’s a little warped at the end. Every time I set my iPhone on the charger, it won’t stop vibrating. Every time it vibrates, it stops charging, then resumes when it vibrates again, and so on and so on. I tried turning the vibrate off, but they don’t give you an option for iPhones. I feel like I can’t charge my phone, because it vibrates at night and bothers both me and my roommate (I’m in college). What should I do???