Slow cranking when hot

[Oaklander]

I have a 1990 truck with the 4.3 liter V6 engine.
I usually drive with an SUV so it's been quite a while since last driving the Chevy. It was at least two months ago. Today I needed to get some stuff moved so I started the truck. It cranked well although I was prepared for an empty battery.
Then I drove about 20 miles to a hardware store. After about fifteen minutes I was ready to go home.
The engine hardly started. It sounded like doing half a turn. Then for a moment it seemed to stop cranking completely. After that it began cranking again and fired up immediately.

What could cause this?

 

[1995sierraz71]

The timing being off could definitely cause that issue. My 95 Sierra was having the same issue. Mine turned out to be the starter, as it got hot sitting a short time with a hot engine, it would crank so slow, I was nervous about if it would start. Hope this helps