Engine unexpectedly shutting off

Some basics you can have done is have the pcv system cleaned and the throttle body cleaned. If you still have issues, you may want to call Volvo to see if your vehicle is covered by the 10year/200k mile extended electronic throttle module warranty? But for this you would need to pay for diagnostic to have them diagnose to see if the throttle is faulty or not? You may just need some software ugrade to it if one is available and which also has an extended warranty of 10years/150k miles. But your first step would be to make sure the pcv system is not plugged up so take it to a shop that actually specializes with Volvo's or you will be paying for something that they will claim they know what they are doing but only just do part of the job. So call around.