Golf Won't Reverse

Hello all, I have a '01 Golf, 4cyl, 2.0litre, automatic transmission that for the last couple days doesn't want to reverse once I put it in gear. I have to either turn the car off and then back on or put it in park and then reverse again numerous times before I get it to reverse. Normal driving is fine and I have no problems with it in Drive, only in reverse. Once the car is warmed up though, reverse works fine. Only when I first start it do I seem to incur this problem. Any ideas? Am I low on transmission fluid like my one friend told me? If so, can I just add fluid? I saw an earlier thread that only the dealer can check and add trans fluid and it costs $70 just to check. I hope this isn't the case. Any help is appreciated. Thanks in advance.

The best thing to do is check the level first.