I have -05 S60 with 408tkm(or about 253k miles) on it. It's been working fine considerig the milage until today.
When I parked it today nothing special, but when I came back and tried to start it the ignition key turned only just enough that steering lock opened, but it didn't turn properly to Position I. There was hard stop every time I tried to turn the key. I tried wiggling the key, another key and nothing. Both keys did the same. Key started to turn and then stopped.
After wiggling and turning I was able to get the key turn past that point and car started normally. When I got home and shutdown the car there was bit of a difficult spot to turn key off. When I tried start again the step was there again, but this time I was able to turn it more easily over it.

Any idea what's causing that 'stop'/'step'? I was thinking that maybe the lock could use some thin lubricant if it has trouble register the key properly even though it lets the key start turning a bit although I'm not entirey sure if that's the problem.

I did some googling and it seems that could be worn lock cylinder. I could try thin oil to to breath some life in it and maybe look for replacement lock.

 

You have a bad steering column lock. It is a common problem. There are possible solutions found online - by moving/removing parts of the bottom of the lock.

A permanent solution is to order a replacement steering column lock from a Volvo dealer using your VIN. The new column lock will be manufactured to fit your existing key and in the US arrives in about 3 days. That way you won't have a different key for the ignition (and have to "program" the CEM to accept the signal from a new key)

 

I was thinking of getting used lock. Maybe switch the 'immobilizer' part of the key from the old one and only use the mechanical part from the new. Do I then have to reprogram the CEM? I looked at the new lock prices and they are more than I'm willing to spend on that part on that car. Maybe if it'd be 10 year newer then maybe and less driven.

I'll check if I can find the video of the 'workaround'. That'd help at least at first.

edit. I think I found the video describing the workaround. I'll try that and see if that helps. Thanks would have not thought that myself.