Others have said this, but I want to expand-

It is likely your shifter, something outside the transmission in the shifter itself, or in the cable to the transmission.

If it is not the shifter, it is a problem with the spring on an internal part called the parking rod detent pawl. It also could be a problem with the internal parking rod. If it is an internal problem, flushing the transmission will do no good, and it does NOT by itself mean that your transmission is about to go out.

Start by having the external shifter linkages checked out. This should be fairly cheap, I am not sure how much though. Next check internal parking rod, linkage and detent. On most transaxles these parts are easy to check just by pulling the pan off, and should again be fairly cheap to check. I am not sure if your transmission will have to come out to replace internal parking parts, but most do not.

Time to service your transmission but unfortunately probably too late. When you go, be sure you go to a REAL place that replaces the filter and doesn't simply do a flush/recycle job. What you are looking for is debree and since transmissions are closes systems if there is anything there it means it's actual parts of your gears and such that you are looking at. Not dirt. Sorry to tell you this but dirt cannot get in your transmission. Start looking now for a new/used or rebuilt transmission. You have about 2 weeks before you won't find reverse.

You mean I have 2 weeks before the whole thing goes out?

It won't do it all the time, just when it is cold outside, I have noticed.

It's a sign and a big one. Get it serviced to check it out. If it's clean and topped off you have a chance that it's something else but don't count on it and you won't know until the contents of your filter are checked. I got an extra week from one just by servicing it and it let me know I had to act quickly. BS on dirt and cold, that isn't how transmissions work. CLOSED system, no dirt and cold is not relevant to parking a vehicle that has been moving. Cold may be relevant to finding D or R at zero initially but that's it. Motor mounts, drive shaft, transmission, one has a problem but if it was motor mounts or drive shaft you likely would be feeling it in other ways. Sorry. Head up can save you tons of money though.

maybe you have dirt in your transmission fluid. Is it really cold where you are? maybe the grease in the shifter is cold and hardening making it delay. does it do this after you have driven for a while?

I think that is what it is. Because it started doing this when it was getting really cold. And it's 23 degrees right now, and I turned my car on, and then went to go put it in park and it's took the longest it's ever taken.

Sticking shifter cable sounds right.

hello Sheldon have your gear shaft inspected it may be out of sync there are ajustments that can be made for this also it could be a cable that is sticking