I hope you meant to write "10-20 seconds of cranking", not minutes. That would be a serious strain on your battery and starter.

My 1995 E420 has had some cold start problems recently. Lots of cranking and a little gas needed to start the car when cold - problem gets better when engine is started warm.

Since I used can of fuel injector cleaner, the problem has gone away. Perhaps it as some deposit build-up? Anyway - it can't hurt to try. Use a 12 oz. can of Chevron Techron in less than 1/2 a tank of gas. Try and do more stop-and-go driving vs. burning the whole tank up on the highway. it's the soaking in between engine starts that helps Techron work.

This would be a cheap place to start before throwing parts at your problem. That's my preferred method of troubleshooting. Cheap first.

Troy
1995 E420 90k