new starter necessary?
 

my son's 86 300e cranks slow for a couple of turns before it speeds-up and starts. Battery (which needed replacement) was changed but problem remains. new starter?

Check battery cables and ground connection at the engine and frame first, but if you don't find anything, have the starter current draw checked. If it pulls too much current, replace it before it refuses to start the car in cold weather.

Peter

Check the starter motor brushes. They may be worn and need replacing. No need to replace the entire starter motor AFAIK.