Please help.

I own a 1988 740 Turbo which I consider to be well maintained.

Recent History:
Complete tune up using premium parts 10,000 miles ago.
In tank fuel pump replaced 500 miles ago.

Part one: For the most part my Volvo runs great without any issues. Recently, I was driving on the interstate and without any warning my engine hiccupped. I thought I was a fluke but then about 10 minutes later the engine cut completely out without any sputter or warning. While staring at my gauge traveling approximately 70 mph the car started up again without any action from me. For the next hour of our trip the car did this. The longest it stayed stalled was about 7 seconds after which the car started again and I thought I saw some sort of sparks dancing on the highway behind me as the car came back to life, this could have just been a coincidence. On this trip all gauges appeared to be normal, my temp. ran about half way.

Part Two: On our way home the outside temperature was considerably colder and the temp. gauge maintained about 1/16th. On this trip the car gave absolutely no trouble.

Part Three:
For the past few days while driving at city residential speeds I sometimes come to a stop and the engine jerks a little and dies almost as if something is not disengaging.

Can anyone help. Thanks!