This sounds very familiar. My '85 CVH 4/4 had almost identical symptoms - would be sluggish to turn over, and refuse any kind of activity whatsoever within about 5 minutes of being stopped. A few minutes' wait until everything had cooled down a bit was normally enough to get me going again, but that's a bit embarrassing when you're in a petrol station clogging up everyone else's exit! Earth straps, starter motor, etc all seemed fine. Replacing the battery, despite assurances that it was OK, has solved the problem completely and it now fires up on the first turn of the crank.
