Why is my volvo surging and turing off randomly.

What is your question?

My 95' 960 Volvo will sometimes surge and/or lag when I accelerate.. It will randomly shut off, but radio and dash lights will still be on.. Check Engine light is always on. Service light comes on when you first start car, but turns off after driving for about 5 min. My Volvo has 90,000 miles. I have had it for a little under 4 years and before that it sat un-driven for years.. Recently changed spark plugs and replaced coils. Thinking next step is fuel pump and maybe O2 sensor? HELP.