We are going to be in Tuscany for a week in September. We have a free day on Sunday and want to know if the shops and restaurants are open in Montepulciano on Sundays?
You will find that restaurants will be open on Sundays - stores are a bit of a hit or miss, some will open and some won't. But many of the more tourist oriented places will be open.
Have a look at this link, you will find some great suggestions for things in Montepulciano (wine and more) as well as some great nearby towns.