cb randomly blasts loud noise... why?

[XHitman396]

so i got an old Cobra from a radio shop that the guy said he ran through and did whatever the hell you do to a CB to make it good, and a few months later, whether the thing is on or off, it just blasts out like a high-pitched, constant ring for about 10 seconds, and i have to hold down the mic talkie-button (yeah i know nothing about these things) until it decides to stop. it's extremely loud and scares the hell out of me every time, and gets a lot of weird looks when i have it on PA. i asked before but i dont think anyone had an answer. any help??

 

[readymix]

Does it have a weatherband? Mine does that when there is a weather alert so I know to tune into the NOAA channels.