....but the car has 170K miles on it right? If you'ld like, you can try bleeding the clutch slave cylinder just to rule out the slight possibility that air somehow got in there but unless the brake fluid either went too low or there's a hydraulic leak (either clutch master or slave cylinder), air would not normally get in there by itself. Do inspect both hydraulic parts for evidence of brake fluid just to be sure. Bleeding the slave cylinder will at least eliminate hydraulic problems as being a possible cause and it's easy to do, best done with a brake bleeded (either vacuum type or power brake bleeder using pressure).
A worn clutch disc will cause the problem you're describing here so at 170K miles, that wouldn't really surprize me alot.
Volvos with hydraulic clutch systems like yours do not have any adjustments. There's then only 2 possibilities, worn clutch disc or a hydraulic problem (fluid leak or air in system).