@noromance The only viable reason I can think of that might cause that would be the spindle oil needs to heat up a little to thin out so the table can reach full speed. In which case I would use thinner spindle oil. Who is to say it is not the cartridge warming up. Theoretically it's rubber suspension might soften with a little temp build up. The cartridge is a transducer as are loudspeakers. Older turntables may drift with temperature but not if they have AC synchronous motors.
I would politely say that if it is your turntable that needs to warm up there is either a problem with the turntable or the noggin.
Audiogon question of the day paid for by @rauliruegas purveyor of fine Mexican Tequilas. Does noromance have a problem with his turntable or the noggin? The winner gets a 7" 45 of the Tubes White Punks on Dope.