Sadly, no - but thanks. Since the problem clears without my doing anything, usually on the next shot, if it is a setting, the fault is somewhere in the circuitry and not my oversight. Also, the D90 is seldom on a tripod and I must admit I have never had the ambition to locate the shutter delay. Thanks for the tip. Yep, there it is, d10. Cool.
Anyway, my working hypothesis is a corroded contact in the shutter button or in one of the associated solder joints that connect it to a board. If a lot of folk experienced this problem then I might have a prayer of having Nikon do something about it. I don't mind the camera having a quirk, so long as it doesn't really get in my way.
For instance, the D70 has lost a few segments of the shutter count numbers on the top LCD but I've learned to translate. Same with its sporadic CHA errors. Quirky, minorly annoying but nowhere near fatal. No camera is forever, but then, neither am I.