Sounds like the glow plugs are on there way out. I get the same message and the engine sounds a touch rougher for a min or so. Before this started I never had any prompts about glow plugs. My indy says there are errors for the glow plugs reported. I'm on 97k, 56reg 335d.
Going to get them done before next winter as they seem that they will last this one out. will also get swirl flaps at same time as its in the same place.