My crt monitor automatically goes to standy by mode with a blast like sound

hello friends,
I have a 15’’ AOC monitor that i have bought 3 years ago ,now it had started to come up with a problem that i automatically goes to standby mode with a small blast like sound then after 2-3 sec it comes back to display mode this happens continuously . now i am quite feared that my monitor can blast.

i have also checked my cpu on another crt monitor its working fine …
that means there’s something wrong with my monitor

please help me guys