I know, take it to the shop. But I enjoy solving as many problems myself as possible. So: '96 with 124k, and the starter is starting to be reluctant, almost as though it's got to think about it a couple of seconds. Always starts readily once it makes up its mind (without backing off and turning the switch on again), and no other problems at this point. What would be your sequence of diagnostics (understanding that I'm only semi-adept). Contacts worn? And if so, is this something I should be able to do myself?
Yeah, the neighbors think it's a hoot to see a little old lady climbing up in the engine compartment to tinker.

 

First make sure the cables are not corroded. On the starter and the battery.

 

One potential cause of this is the relay in the power distribution center ("PDC") under the hood on the driver's side fender well. There's a legend under the lid that tells you which relay provides power to the starter -- swap that relay with another like relay that is part of a non-critical circuit and see if the problem clears up. If it does, buy a new relay to plug into the starter socket in the PDC, returning the relay you use for testing back to its original location.

With any luck this quick and easy test and fix will cure the problem.

 

in addition to the above, if the battery is weak it can sort of bog and delay rotating the starter. you can get a load test on the battery for free at any parts store. you can accomplish your own load test by turning on the headlights, brake lights, etc before hitting the starter. if the battery is weak it'll really bog, might even start clicking and not turn at all.

if its none of these things, then its likely the brushes in the starter that have worn out. with the age of the truck its about due for a starter. you can get a rebuilt one with probably a lifetime warranty at autozone or advance. 2 big bolts, 1 big wire, and one small electrical connector. disconnect battery while replacing as the big wire is 12v live/hot.

if you're curious about how a starter works, disassemble it and locate the brushes which ride on the shiny copper commutator. use a screwdriver to scrape any carbon buildup from the slots in the comm, replace the brushes and it'll last another 10 years.

 

Worn contacts maybe? http://www.4crawler.com/4x4/CheapTricks/Starter.shtml