That is usually caused by a tired ancilliary belt (the one that drives the alternator etc) - as the rubber ages, it grips less well and slips more against the pulleys, especially when cold and damp. After a couple of minutes it dries out and warms up, and so stops slipping.
The timing belt itself is toothed, and so cannot slip (it would cause a catastrophic engine failure if it did), and if the tensioner was failing I'd expect the noise to be constant.
Replace the ancilliary belt (very cheap - the one for my car is £6 (~$10), I'd expect a Volvo one to be similar). If that doesn't fix it, it could be something more serious, but that seems unlikely to me.