Mine does the same thing, although it misfires on 2 cylinders if it's freezing outside, 1 cylinder if it's 50°F. (30 - 45 second glow).

I think it's a combination of an extremely stretched timing chain, a bad glowplug, and the need for a can of diesel purge.

Plugging in the block heater all night makes it happy, and it will run on all six with 15 - 20 seconds of preglow. The block heater will make the temp gauge register at 40°C when the outdoor temp is freezing. Outdoor temps of around 50°F will make the temp gauge register 50 - 55°C.

It's time for some maintenance.