Our car has 43,000 miles on it, It has been acting up very random for 9 months now, been to the transmission shop 4 times to find the problem:

After the car has been started for the day and it is parked, time parked doesn't matter, you start up, put it in gear, and rather than the smooth transition, it is more of a thunk, and you know without moving an inch it has kicked onto limp mode. This may only last a few blocks, but it may last miles before it suddenly works perfect again. Sometimes days only between occurrances, but sometimes weeks. After you shut it off and restart the check engine light will come on. It will cancel itself within the day, the codes saved in the computer are pretty basic, of no help,will try to get them.
miles driven play no factor either.
really like the car though.