I have a Seagate ST3320418AS in an external Coolmax enclosure. The enclosure is powered via wall-wart, and the data connection is eSATA.
The odd behavior: When the drive is in the enclosure and ONLY the power is plugged in, it spins up as expected when powered on. If eSATA and power are plugged in, the drive does not spin up upon powering-on the enclosure.
I have tested this drive in an identical Coolmax enclosure and the behavior is the same. Any ideas?
The enclosure's internal control board probably is just set to spin up when the signal from the host computer comes down the data cable to Initialize the unit as part of the overall POST process. By default, it also is set so that, if there is no data cable connection to a host, it will spin up anyway.
I do no think the behavior you describe is a problem at all.