Hi, I have same problem on my03. This has been an observation on last 3 mots.
Next service and mot in July and if if it gets through with not too much effort, I may treat it to two new headlights.
You need to check what type of headlights, but mine are early halogen.
In my case you can purchase OEM headlights on eBay which are new but not genuine Volvo, for about £100 each.
https://www.ebay.co.uk/itm/303236694809
Simple to fit and no programming required.
You can get kits to clean them by rubbing down with very fine emery paper (1000, 2000 and then 4000 and can get them pretty clean but you must overspray with clear laquer otherwise they deteriorate very quickly.
I have done mine twice in last four years but they are now quite marked.
Hope this helps
John l