It is very likely that you are feeling a rough downshift to first gear as you slow down to 10 mph. This will tend to happen when the transmission's fluid level is low, but I have to assume that you have checked the trans fluid and ruled out this simple fix.
But--perhaps even more important is this question:
When was the last time that you had the transmission fluid changed?
If you have not had this done every 30k miles, then it is likely that your transmission is nearing the end of its life. Transmissions that are not serviced on that type of schedule can fail any time after ~100k miles, and failure is pretty much of a sure thing by ~150k miles.
I would suggest that you take the car to an independent transmission shop that has been in business for at least 3 years, in order to get their assessment of the symptoms and the condition of the trans. Whatever you do, DO NOT go to AAMCO, Lee Myles, Cottman, Mr. Transmission, or any other chain operation unless you want to be told that you need a new transmission--whether you really do or not.