iphone wont stop vibrating

So my iPhone 4 randomly shut down and i thought it ran out of battery so i plugged it into the wall charger and it started vibrating. It didn’t stop vibrating until it ran out of battery around 4 hours later. i have tried holding the power and home buttons and letting it die all the way down and then recharge it but it just keeps vibrating. i bought a new battery and it still vibrates. Any ides until i spend $260 to get it fixed?

Thanks