They offer free diagnostics. My car started like that and eventually wouldn't reverse at all so i had to have the trans rebuilt. Of course different cars can mean different things, but it doesn't cost but about an hour of time to have them take a look.
On an issue like that I would definitely let the pros look at it. Make sure when you discuss it you let them know was it cold outside, wet and if it was early morning of after driving for awhile. Good luck.
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