"I walked up to start the engine, reached in through the open door (shifter
at neutral) and turned the key.  Nothing.  Then again, nothing...[and now]
it started right up."

Skip,
I did, twice, play a similar game.  But first, just confirming -- no clutch
micro-switch, right? (IE the starter does not have an interlock on the
clutch, right?)

Personally, I'm not keen on the stuck-clutch theory as you were in neutral
anyways.  (The starter motor is strong enough to give the whole van a hard
bump should you try to start it in gear, clutch engaged.  Don't try this in
proximity of any other vehicles!)  On the other hand, maybe I just don't
understand.

Double your fun:
Try repeating the no-start procedure (IE. try reaching in through the
window to start it in neutral with the clutch engaged.)  Then go from there.

In a previous van (a grey, 1990 Westy, widely referred to as "the van,
man"), dating back about 13 years ago now, so details may be iffy:
Flaky starting.  Ultimately found that the large wire (6 gauge?) was coming
off the heavy lug that attaches it to the end of the starter.  Resolved it
by depending on a low-quality jumper, covered in electrical tape, to make
the connection.

Forgot about it and it lasted until -- get this -- 12:05 AM on Dec 26 just
north of Barrie, Ontario.  At that moment, it was blowing tons of heavy,
wet snow.  Here is how it went:  Gas station attendant locked up and turned
off the lights.  Deep darkness and satisfaction filled "the van, man" due
to mother natures' obvious support of my wintry adventure.  I reached for
the key and turned it -- nothing.  Eerie hush of snow falling -- not even a
click indicating a dead battery or failed starter.  Luckily, I remembered
my botched job and was able to fix it (poorly) again in a few minutes with
snow drifting down my neck.  It stayed that way for another 100,000 km
until the starter failed, just the month before a road trip from Toronto to
The Gunks (near New York city) with fellow dirt-bag climbers.  As it was my
daily commuter, I didn't have time to fix the starter, obviously -- there
was time only for rock-climbing, mountain biking, a bit of work, and tons
of eating garlic, onions and oats.  So I bump started it for a month, and a
road trip, and fixed it when I returned.  Miss those dirt-bags.  Shout-out
to "the van, man", where ever you are.  Hope your owners treat you better
than I did.  I'm sorry, van.

Gabby
'86 Westy (Miss Betty)