V70 Intermittent Starting Issue

Check for a defective fuse, especially those related to the ignition circuit. Does the starter motor engage when it fails to start?

Where would I find the ignition circuit fuse specifically? And how would I tell if the starter motor is engaging or not?

Consult your owner's manual for fuse box diagrams. If you don't hear a distinct 'click' or whirring sound when turning the key to start, the starter motor probably isn't engaging. But, given the engine shutting off while driving, it's probably best to take your car to a workshop.

You nailed it! Turns out it was a defective fuse, just like you said. Replaced it for 52€ and she's running like a charm again. Thanks a million for pointing me in the right direction!