There has already been a few postings about turn over, won't start, has no compression on 850's. This always surfaces in cold weather. The thing that almost always preceeds this no run is that the car was started and run a couple of times, each time for less than a minute. This does two things: 1. it sets the stage for fouled spark plugs, and

2. it leads to the normal exh valve stem lube oil deposits getting partly dissolved and forming a sludge (GOO) that makes the valve just sluggish enough to allow the hydraulic tappets the opportunity to fill ("pump up") and hold the valves off seat 1 mm or so as the cams rotate and moves the valves up and down.

Starting an engine and running it for a brief period IS NEVER GOOD!

The engines maybe are punishing you for doing this by not running.

If you need to start a car to move it in the driveway then start it and let it run for several minutes until it is warm. Better would be to start it and drive it a few miles if you have any reason whatsoever to do this.

I had a 96 850 do this to me once when I had mistreated it to a couple of very brief crank up and move cycles followed by it failing to run the next morning when I was in a rush to get to work (it showed me, huh).

I deserved it. That was outright abuse.

Volvo and many other car makers with 4 valve per cylinder hydraulic tappet engines (Volvo quit using hyd tappets in 2000) have had this phenomena in their cars. They started using more foul resistant spark plugs due to better plugs firing when the compression is low and just barely averting this trouble. Most of us will not have it happen, but if it happens to you then you caused it. The car didn't just up and decide to not to have compression enough to run that day for absolutely no reason............

Enjoy and be kind to your motor and it will be kind to you.