It might be one of the components (capacitor?) ageing in the soft-start/speed control circuit. If it gets worse you might need a new module, as they tend to be potted in resin and not practical to service. It might actually get better with use, as electrolytic capacitors can self-heal in some circumstances.
If you change the speed when it's on, does it do that smoothly, or kick sometimes as you turn the thumbwheel?
Keep an eye on it and look for a mail-order Freud spares supplier meanwhile. If the speed control/soft start does go, it's not a terribly complex repair (or shouldn't be) anyway, as long as you can get the module. They aren't dreadfully reliable (the speed controllers), as they're very much built down to a price.
They really don't like damp, nor excessive periods of very dry heat. Household room temp and humidity is best overall - goes for anything with a brushed motor and a speed control really. It used to be a common problem with analogue electronics - in damp or very hot dry conditions (such as being on for long periods of time (years)), tracks would crumble away. It's one reason why volume knobs go crackly.
As a general "care+feeding" rule, don't leave the speed setting anywhere in the middle of the range. It's good practice to turn it to the fastest setting when you're finished with it. This means there's no point pressure on the middle of the pot's carbon track whilst it's being stored. Also, if any damage does happen, it'll be in the area least important. I say 'fastest' because cutter speed tends to be more critical on slower settings, and you'll want to protect that bit of track as much as possible.
Hope that's useful.
E.
PS: I have an old audio mixer that spends most of its life in its flightcase these days. It's got around 200 pots on it. They're all stored set to the end of the tracks (faders too), and amazingly, although it's around 30 years old, nothing's gone significantly crackly. Faders should be left fully "on" for long term storage, incidentally.
