1995 s500 intermittent reduced engine power

[gcg]

My car has 110,000 miles and is clean and smooth running, but I have recently encountered an intermittent low power when I attempt to accelerate from around 50 mph. Last week, my car would not restart after the engine was turned off for about 30 minutes. However, I was able to restart it the next day and had it checked out at the MB dealership where they told me that I was due for replacement of the distributors and rotors. I checked the distributors myself and cleaned some of the metalic points because they did not appear to be extemely worn, and I have not had another start-up problem. However, I am now getting the intermittent problem with power loss during acceleration.
Is there a problem with my not having replaced the distributors and rotors, or is there some other problem with the ignition or fuel injection system? What would be the recommended diagnostics for me to do?