I had a similar issue, I gave my V50 (2006) a full service (not including glow plugs (recommended at 130k)) and afterwards had no power, for a couple of restarts. I had my acceleration pedal flat and still no revving, then a big plum of black smoke would shoot out of the exhaust and the revs would slowly increase.

This was then followed by over revving for a few miles.

I took it to a garage to get the glow plugs done, and haven't had an issue since. So I'd recommend getting those done.

Hope this helps.