My 98 S70 T5M did this once about 3 months ago. I had driven about
2 miles (car was cold when I started) and it stalled at a light.
It was very difficult to start -- almost like it was flodded. I also
had a check engine light on after that. I purchased an OBDII reader to
read the code. The code indicated something wrong with the turbo over
boost circuit (I can't recall). I decided the code was not related to
the problem.

I have not had the problem since. It was very strange and unnerving.
I have not noticed anyone else reporting this (here on this board).

I think you should have the OBDII system read for stored codes. I
understand some auto parts stores (pepboys maybe) will read the codes
for you for free.

There was also a recall for the wiring to the throttle positoner switch on
98s. The repair involves tieing down the wire to the throttle positon
switch so it can't vibrate. If that was done it is very obvious because
the wire will be looped back a bit and a cable tie will be holding it in
place. It was called "Campaign - MAF Connector Loose". TSB 2230010
described the repair (my car had this done back in 98).