That sounds similar to how our V90 sounded when the starter failed. What happened in my case was the starter pinion did not fully retract, the screeching you hear is actually the starter pinion hitting the ring gear on the flex plate! Ours did this intermittently at first, and then more frequently until I finally figured it out. I initially misdiagnosed it as belt tensioner and pulley noise. Only after changing tensioner and idler pulley, and subsequent complaints from driving wife, did I realize the problem was not fixed.

Does it happen right after starting the car? Does it sometimes go away entirely?

Listen from under the car near the bell housing and you may hear a metallic clanging/scraping sound.

Replacing the starter on a S/V90 isn't the most fun job I've ever done, but it is fairly straight-forward. I did mine from underneath the car, without pulling the intake manifold.

Andy R.