I think the a/c has been off but I'm not positive.

Someone suggested that maybe it could be the starter trying to restart the engine. This would be consistent with the type of sound I'm hearing.

The starter is "automated" to the extent you turn the key and the electronics decide how long to crank the engine. Any idea how the sensors detect if the engine is started? Could the relevant sensor be impacted by the length of time it was sitting (or the temperature?).