Where do we start?
You need to ascertain the following information:
Are you getting gas? Fuel pumps (there are two. Fuel pump relay? Fuel pump relay fuse?
The fuel pump relay lives behind the ash tray in the center of the dashboard. The fuel system fuse is Number One in the fuse panel. Sometimes the relays go bad. Sometimes the fuse doesn't make good contact.
Are you getting spark? Disconnect the lead from the coil to the distributor and have someone crank the engine while you hold the wire by the insulation near an engine ground - any metal part. No spark means no go. Look for an ignition problem. The coil wire or coil might be suspect.
If you get spark from the coil wire, the distributor might be the culprit, such as a bad rotor which is not distributing the spark to the spark plugs, Remove one of the spark plug wires and hold it near a ground while someone cranks the engine. If you see a spark, the ignition system is working.
The engine RPM sensor, mounted on the bell housing on the passenger side of the engine compartment could also flake out and cause no ignition/ no spark.
Sometimes bad grounds can play havoc with the ignition system and the engine control modules. Look on this site for detailed info on correcting grounding problems.
The engine control modules can also go bad intermittently and leave you dead on the road.
If you smell gas, the engine is probably flooded which means it will have to dry out or you will have to change the plugs. Flooding often is caused by no ignition to fire the cylinders.
Does the no-start condition occur after the car is warm or when it starts cold? Engine temperature sensor perhaps.
My 740 has over the years developed all these no-start issues, which I have resolved by some basic diagnosis. Usually I can get it started eventually and drive it to my independent Volvo mechanic and tell him what I think the problem may be. HAving it towed dead to a mechanic and saying “fix it” could be hazardous to your wallet. You should have an idea what’s wrong before you bring it in or tow it in.