there is a known issue with the 01 auto trans,
slow to engage in drive from R or P.
it may be your issue but usually it develops slowly,
the ''fix'' for the 01 is to add a bottle, 1 qt., of Trans-X slip stop additive the ATF.
usually you do this with a drain and fill,
replacing a qt. of trans fluid with a qt of trans-x .
the fis lasts about a year,
then you have to do it again.
i hope this is your issue and your fix.
having said that,
make sure your trans fluid is full.
the dip sticks are really hard to read.
check both sides.
check it when cold with the engine off just to get an idea if you are in the ball park.
then check it with the trans warm and running.
wait a while after you pull the dip stick,
so any ATF in the dip stick tube can run back down into the trans.
these dip sticks are really hard to get a correct reading.
tip: the difference between too low and full is about a pint.
what happens if you shift into 3, or 2 or 1?
any recent work done just before the problem started?
like trans flush? rad replacement? timing belt? leak repairs?
anything that might have involved the trans cooler lines .