I have a 2000 SLK230 with 215,000 miles. Ran fine last time I drove, a week or two ago because of the ice.
Went to start it, you know how the car cranks automatically when you twist the key to start? Now, it very consistently cranks for about 2 pistons - about two seconds, and then stops cranking. Every time.
It sometimes starts like on one cylinder, bangs a couple times or backfires quietly once.

Plenty of gas. 45 degree air temp, not too cold. Gave it some starter spray, it tried to run on that for a second.

My best guess so far is that the computer is detecting no fuel pressure and turning off the cranking. I hear all sorts of humming that I assume is the fuel pump.

Put it on a battery charger, but that wasn't the problem. No Check Engine light.

Any ideas before I have to tow it to the dealer? Thanks for your help!

David