More then likely an injector issue. With 190,000 on it the injectors are probably about due for replacement. With trucks like service trucks and boom trucks they are usually idled a bunch, so I'm sure it has a ton of hours on the engine also.
It's very common for Powerstroke engines that use a HEUI style injector to have a miss cold that goes away when warmed up. 6.0's are more prone to this then 7.3's due to the injector design, but 7.3's will do the same thing. The term for it is injector stiction.
Only other things to check out for hard starts/rough running would be make sure your batteries are in good condition, the glow plug system is working properly, and you have good constant fuel pressure. If those all check out then you will need to have someone plug into it and do injector buzz and cylinder balance tests to isolate which injectors are acting up. You can try and figure out if it's only one or two injectors acting up, but with that mileage you'd probably be better off just doing all 8. The truck will run much better and you won't have to mess with injectors for another 200,000 or so miles.