I wonder what the compression is like, how many miles on the engine and did it have any smoking under cold starts? Are the valves tight? when was the last valve adjust?
A good engine when warm will start with no glow plugs, or will act hard to start but eventually will start after some cranking.
Logically there is nothing normal about what you described. There is no flooded condition that carburetor cars can have. You flip the starter and a hot diesel engine should start right up.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!