91 Pathfinder - Sometime won't start

I drove about 3 miles after dropping a trailer off and stopped for a sandwich. Afterwards the SUV wouldn?t start again. I had parked on a slight incline and was able to roll backward fast enough to get the engine started. Later, while driving on the highway, I noticed the dashboard meter indicated the charging system was working fine. The following morning I was able to start the engine twice with a few minutes in between. On a third try it stalled. I had the battery tested and it’s good - fully charged.

Turning the ignition key produces a single tick sound, the engine does not turn over.

Does anybody have any idea what the problem might be and how I could go about proving it?

If the charging system is good…then look for a bad connection or bad wires. If those are fine then it could be the starter.

Also look at the current switch in the starter solenoid. This seems to happen a lot with Toyota starters but Nissan starters are designed the same so they may suffer the same failure mode. The high current contacts and disk become worn over time and will not complete the connection reliably. Alternately it could be just a worn out starter itself. Starters do have brushes and bearings that wear out.

Hope that helps.