mm wrote:

My whirlpool washing machine, quite old, needs a nudge to start
spinning, after which it works fine. This means the belt is loose,
right, and needs replacing, right? (IIRC, there's a belt.)

If the motor is running at normal speed when this happens, it could be
the basket drive, which is a clutch mechanism. It may be possible to
fix it by tightening it by installing or removing a washer.
www.appliancejunk.com should have manuals.