2000 Ford Taurus

My vehicle is in the shop as I type this question I feel like I am being taken for a ride my car went from being drivable to not being drivable within 3 to 4 days. When I noticed that there was something not right in the transmission the first thing I did was check he fluid level which was good and it was a nice clear reddish color then the next day it started to get a little worse but the fluid was still the same then as far as the next day I was driving and what happened is I pulled into the gas station to wash my windshield when I put it back into to gear it would not move so I moved it into a different gear and it started to move and then the day after that I drove my vehicle for about 15 minutes and it stopped moving I turnned it off and sat for about 30 seconds and turned it back on and it went into gear and worked so the question would be what would cause my vehicle to do this and why is it that when I turned the car back on it would go into gear and work please help I am confused and need some advice before I make a decision on what to do with
the shop they are telling me that every component that everything inside my transmission is garbage