Sounds like it is a glow plug problem. What are the ambient temps in the morning and throughout the day. Are they close to the same? How long after the first start/drive will it sit before restarting?
How many miles are on the truck. could just be the relay and not the actual glow plugs.
You can test the relay to see if it is dropping to much voltage.
it is on top of the motor behind the ac compressor. there are 2 relays. The first is for the AIH system. The second (furthest from the front) is the glow plug relay
the wire with the boot is the feed wire (bat). The wire "circled" is the feed to the glow plugs.
hope it helps