Need a bit more information:
- What maintenance has the car seen (what has been serviced or not service to this point)?
- Other than not wanting to accelerate, have you noticed anything else out of the ordinary (rough idle, excessive shaking, etc.)?
- Does this happen at low speeds, high speeds, etc.?
- Does that problem happen for the whole day the car is run, just for a couple of minutes into the drive, etc.?
- Any significant event that precedes this behavior (car sits overnight or longer, just filled up the gas tank, etc.)?
- Any check engine light during this time?
There are quite a few things that could cause the behavior that you've described. Many are maintenance related, could need anything from new plugs to a good throttle body and MAF sensor cleaning. Could be transaxle related or just a bad tank of gasoline. Given the mileage and age - I'd look into having a comprehensive tuneup down, if you havent already gotten it done. That will take care of the most likely culprits, like - clogged air filter, clogged PCV valve, vacuum leak, dirty MAF/IAT sensor, gummed up throttle body, faulty coil on plug modules, dirty fuel injectors.