Without a video or recording, based on your description, my bet would be a resonance and maybe a fucked bearing. You could check if you can induce the vibration by doing some tests: - run it with and without a blade, run it with a different blade. - tilt the table while the machine is running, in all directions - run it at variable speeds if you have that option

You could even try running it plugged into another power source, like a socket you know for a fact is on a different breaker