Could be time to clean and re-lubricate the main bearing ;--) And I have found the best sh!t on the planet (in terms of blackest audio background) is van den Hul's spindle/bearing oil. It contains suspended particles of zirconium oxide which act like microscopic sized ball-bearings to keep the metal surfaces from making contact -- this is especially important in belt-driven TT's where the bearing is always being pulled to one side.
.
.