Thanks for your help, Franklin!

I will check all what you've said.
Maybe I can give more info: the car has about 88,000 miles, year 1997.

I checked the fluid on level surface, but in P position, normal operating temperature and it was normal. Also no smell, normal colour. The fluid was changed about 10,000 miles ago, together with pan filter.

Today I drove the car around for about 5 minutes, just to reach working temperature of motor. I don't know if this is enough, but I checked the fluid in transmission like you told me to and it wasn't hot.

What I can say is also this: the car is not working normally in idle as it should: it's shaking a bit. I thought it was because of water pump replacement and that timing belt wasn't correctly installed, but the mechanic opened it again it it has virtually no deviation (1 milimeter). You can also feel the car want's to move, juuuuust a little bit, but it doesn't have "power" to move. As I spoke to other guys, the diagnosis might be some switch or lamellas in transmission (at the clutch or something, I don't know I am not mechanic).

Maybe any new idea or opinion?

----------------------------------------------------------------
Problems are, problems will be, who gives a duck.