Does stopping and starting effect my walking workout?

It is actually a great way to build intervals into your walking work out. Walk briskly for as long as you can and then rest or walk slower for a short period, when you are ready walk briskly again. Walking is a great way to get active!

Absolutely, you are doing a form of interval training by taking your heart rate up and down. It is a great mix with your normal day of continuous aerobic activity.

Stopping and starting your walking workout can be viewed in different ways.  If you are completing intervals where you walk at a brisk pace for a period of time and then slow yourself to a walking pace then yes, loads of benefit will be present.  This form of interval training will assist in bringing your heart rate from a high intensity to a lower intensity to help you burn more calories.  However, if you are going from a full speed to a complete stop then this will not be as beneficial.  You need to keep yourself going to avoid any blood pooling of any sort.  Blood pooling is the result of abruptly stopping exercise prior to bringing your body back to a relaxed state.  This may result in swelling of the muscles.  Essentially you should keep yourself going and prior to coming to a complete stop, be sure to cool your body down with some form of stretching.