this is a sign of premature pnp failure. There are many many post here regarding this issue. Your solution is to put the key into postion 2 (dont start the car) and to move the gear shift from R to d1 and back to R around 20 times or so quickly. This is a short term remedy.. It'll probably give you a year or 2 before the PNP will have to be replaced. Worsenling (sp) signs will be that the flashing arrow will be more frequent and it'll go into limp mode which will make the transmission start off in 3rd gear instead of first.
Also a sign is the reverse lights will no longer function.