I don't have an MTX, but another post mensioned the master/slave in the clutch system.
Assuming the systems are similar, I had an old Mazda RX-3 that did this. The seals in the clutch master cylinder were going bad, the aluminum surface inside was also getting pitted so fluid leaked past & the clutch would slowly engage no matter what. The hydraulics for the clutch & brakes were separate in the Mazda.
It was not difficult to replace them with new units, but there was a LOT more room under the hood than on the 'Tour.
Anybody else???