I've been having an intermittent ignition problem for the past few months too, and though I use a 940 GL, my problem may have a similar background: here's what happened with my car, and how my resourceful neighbourhood mechanic seems to have fixed the problem.

My car would intermittently refuse to start: engine would turn over, but not come alive. Once the car started, it would run fine. This no-start occured every few weeks initially, then got more frequent, but each time once started, it would run fine until one day it just died while driving (I was stopped at a set of traffic-lights waiting for the lights to turn, engine just died). Each time a no-start occured, the car would start after waiting an indefinite period of time, usually about 15 minutes.

Called in mechanics a few times, essentially they were just scratching their heads unable to diagnose the fault. I put off sending my car to the Volvo people 'cos over here they have a reputation of just basically ripping you off changing all sorts of parts and charging exorbitant fees.

Anyway, to cut a LONG story shorter, this mechanic has a look at my car, and fixes a bulb at the end of a long wire.....one end to the +ve terminal of the ignition coil, the other end ground to some other part of the car.....and turned the ignition to the Run position, noticed that sometimes the bulb would light up, sometimes it would not, and whenever the bulb was lighted, the car would start and whenever it was not alight, the car would not start.

So he now knew that "something" was preventing a +ve signal reaching the ignition coil, but just what was this "something"? The Radio Suppression relay was a suspect, as was the Ignition Power Transistor, but changing the Radio Suppression relay didn't fix the problem, and anyway the mechanic decided to have a look at the main fuses and relays , and started gently tapping them...while looking at his test-bulb (a long length of electric wire and a simple bulb, to hell with all them fancy meters and gizmos!), and EUREKA! gently tapping on the Ignition Relay showed it was slightly loose-fitting, sometimes the bulb would stay brightly lit, sometimes it would be off.

A bit of judiciously-placed solder on the relay's contact points to make it fit snugly, a bit of gentle tapping to test the bulb stayed lit.....and problem seems fixed!

I'm not saying it's your ignition relay: just that if you had the bulb-on-a-wire thing, it would help troubleshoot in a simple but no-nonsense way. Or at least help find out if it's just some simple intermittent-contact thing.

have a nice day,

Raggy