could it be a stray static electric discharge phenomenonmenem??
More like the capacitance of your hand next to the lamp. Why that is different than the metal reflector I don't know.
I think all these problems are due to the energy saving design of both the ballasts and lamps we have nowadays, possibly the low mercury content also. Seems to have started when these became required. Looks like the starting on these things is very marginal. Years ago when nobody cared how much a fixture consumed or the mercury content they seemed to start much more reliably.
When instructions say that the lamps must be within 1/2" of the grounded reflector they are saying that the reflector must be connected to the ballast case not an equipment ground. Many people have this misconception. Of course the NEC requires an equipment ground, but it is not required for the fixture to light. Plenty of shop light fixtures out there with 2 wire cords.
Anybody with finicky fixtures should consider what I said above. Nobody thinks of trying another manufacturers lamps but that may be what the problem is.
-Hal
