iphone 2g vibrates when i push the screen. help?

[LilZain03]

i have an iphone 2g 3.1.2 and when i keep it on vibrate and when i 'push' the screen the normal symbol and vibrate symbol(with the slash) comes on and flickers back and forth on the screen but when the phone is on normal and when i push the screen its fine. i think the phone thinks that pushing the screen goes to vibrate then goes back to normal. is there a way to fix this? thanks