2004 Chevy Truck Starter Not Starting (sometimes)

[PILOON]

So in my experience those trucks, especially in corrosion belt areas, have battery cable issue and like said above connection issues.

Yes. I also have seen cables so corroded that they bloated almost double size. Rare but also fairly visible.
The result is that you lose a large portion of the current carrying capacity.
One check is that the cable will not be as flexible as it should be and repeated flexing will actually fail it completely. Also at ends there generally will be a white powdery residue.

 

[MossRoad]

The majority of starter problems end up being contacts.
Either the battery terminals or the grounds.
You want shiny metal to metal TIGHT contact.
A wire brush to ream the posts and sand paper (shiny metal) for the grounds.

The next culprit is the ignition switch itself. Generally they have a dielectric grease inside to lube the contacts. That grease (in the cold) gets stiff or dry and prevents contact.
Squirting a bit of WD40 into the key slot is a great cure.

Naturally a good battery is assumed as well as a good starter. Either way the above measures proves out the system integrity and possibly saves you a starter and or battery.
(have known folks to replace both items only to find that the earlier simple tricks would have cured hard or no starts. Plus store will not allow returns on electrical stuff)

Might add that a squirt or 2 of WD40 on the bendix sometimes frees up the bendix.

I don't think there are any contacts in the key slot on the OP's vehicle having to do with ignition. The key turns and operates linkage that operates the ignition switch that is located further down the steering column. Its a sealed box. At least that's how I recall it.

 

[SandburRanch]

Before spending money on a starter like I did once, try a different battery. I had a battery that would intermittently loose connection internally. All attempts of jumping from another vehicle failed. I realize it seems strange but battery replacement solved the issue.

Or how about one that dies when turning a corner to the left but not right. Once again, the battery.