Intermittent start issues

When I start up from cold, it usually takes a 3-50 tries. Once it's warm, it usually starts on the first try. When it doesn't crank, which is the issue, I just hear a click, from what seems to be the solenoid. Is my starter solenoid going out? Can I repair it, or redneck repair it? Jumper it? Thanks guys

[1983 b2200 diesel]

Is this the part I need?

Check your battery, even if it's 3 months old, try a jump start, etc. Measure and post voltage across the battery terminals while it's in the clicking "no-spin of engine" mode.

Because I'm thinking battery if all your terminals and connections are clean.

Fixt! Filed, sanded, and scraped to a polish the battery connectors, battery clamps, and some ground connections. Starts right up. Auto store guy said I needed a $150 starter, so total score! Thanks so much Cusser.