I know I have very little detail here but it’s worth a try to see if anyone has any suggestions at all. My 2006 S60 is making a sound coming from under the hood when it is first started for the day. After it warms up it goes away. It sounds like a belt rubbing or something but the frequency is very low, like every second or two, so it doesn’t seem like the accessory belt since that is spinning too fast to be the right frequency. I was thinking power steering pump, but my fluid level is good and the sound doesn’t change if you turn the steering wheel. It is definitely something driven by the engine, it isn’t an electrical sound. No performance issues are evident at any time. Doesn’t change with increase in rpm. Also is not affected by the a/c being on or off. I’m just waiting for something to break.