I've got a 1994 3000 GT, bought it new. Been great for 22 years and used only in summer yielding 76,000 miles on it.

You've got a dodgy cup in either the master cylinder (at the pedal end) or the slave cylinder (at the engine end). Internally, they are basically built like an old-school bike pump, with a rubber cup that slides inside a tube. As the cup is pressed down it squirts fluid out, into a metal tube and into the slave cylinder (which is then forced to open up). The opening slave cylinder runs your clutch (disengages drive). They often show a few signs of leaking when they are about to dog out (which yours certainly IS). Using a stethoscope (or just a rubber/plastic tube in your ear) you can sometimes hear them "squish" as they leak pressure, but unless you are going to attempt the repair yourself.... get thee to a mechanic ;)

Sounds like master cylinder may need replacing. But at its age I would replace master cylinder, slave cylinder and the rubber hose that connects the slave cylinder to the firewall piping. Not that hard to do if you a little mech inclined.