What causes radom throbbing and swelling in a women's left foot?

Hmmm: Sometimes nerve entrapment can cause symptoms like you are describing; or poor circulation may cause this. Best advice is to get to your primary care physician and have him/her examine you. Best to get an official answer to a random problem; and get the appropriate treatment.

Circulation: There are many circulation problems that can cause leg pain or throbbing or swelling. It shouldn't happen just to a left foot specifically. Have you had any accidents? Fallen? You can start with a foot doctor called a podiatrist. Then, if he doesn't find anything- you can be referred to a phlebology doctor: www.Phlebolgy.Org and put in your zip code. Venous disease causes swelling, cramping too.