The spin-up/spin-down is default failed RD53 behavior (Micropolis 1325).
The two reasonable explanations I've collected suggest that the head
bumpers break down over time and the head assembly sticks eventually.

The one I feel is most like though is that the electronics on the drive
has self test hardware that detects that the motor is over-current when
just up to speed and shuts down. We've been through tons of old RD53's
and our hardware folks even told me they could show me where the current
test circuitry lives on the board so you can fool it, but only for a time
before things get really bad again and you're out of luck.