Once again, the hedge trimmer failed to turn on with the switch pressed, so I took it apart, did nothing, and had thing start working again:
It finally penetrated my dim consciousness: perhaps the switch is fine and a carbon brush (or two) has lost contact with the commutator atop a layer of oil and dust.
So a year from now when this happens again, try jamming a screwdriver through a vent slot and moving the motor a few degrees to jostle the crud.
If it works, that would be much easier than taking it apart!
The Smell of Molten Projects in the Morning 
If your memory is anything like mine you’ll forget next year until you’ve taken it apart (again). You could write yourself a note – but would have remember to affix the note to the trimmer at the end of the current season.
Perhaps untrimmed hedges will be the Next Big Thing.
Ah, but I have an external memory: whenever something wakes up dead, I search my blog to find out what I did (wrong) the last time …
I’m definitely in favor of the “forever wild” yard care technique, though.
Suggestion: Try a blast of compressed air before resorting to a screwdriver. Probing with a tool could result in collateral damage.
That would poot an unimaginable cloud of dust over the entire Basement Workshop: better to threaten it with a screwdriver and a Bad Appraisal.
I have a 20+ year old Makita 4″ handy-grinder that seems to have a bad spot (open winding?) on the commutator. If I rotate the grinding wheel a fraction of a turn, it will start. OTOH, I now have a Makita 4.5″(!) grinder that’s not as handy, but starts all the time. I’m not sure if the wheels for the old one can be used on the newer; haven’t used it that much.
I keep the old grinder for rough work outside. Never could talk myself into getting one of the big 7″ two-handed grinders.
The reply from RCPete brought back a memory from the late 1970s…
My dad had a business in an old building… The ventilation fan mounted in a upper window was almost as old… (I climbed up there once to look and the manufacturers nameplate had a date of 1932 on it)… and the motor had a spot that occasionally wouldn’t start… the motor just hummed.
I distinctly remember my dad taking a 8 foot length of 1 inch conduit from a closet… it had a 90 degree sweep bend on one end… he held the bent end upwards and pointed at the fan blades… he’d send a long blast of air from the compressor hose into the lower end of the conduit… just enough to bump the fan blades a little… and the motor would start.
Mike
Sounds like the same problem.
However, if poking the rotor with a sharp stick starts it up, I hereby swear a mighty oath on the bones of my ancestors to never again open the housing, even to satisfy my curiosity by measuring the commutator windings.