Lost power, could be engine or transmission weak

First check all fluid levels, like ATF and oil. If these are correct, tune up may be needed.

Keep in mind, when a car is 18-year old, powertrain is worn, it will lose power and eventually come to the end of road. Do a regular maintenance, but don't spend too much money on it, cuz it may not worth it before you start to look for a new car.