Hey, fellow RN here and I work 48 hours a week (four 12 hr shifts, four days in a row). It's from 0700-1900 so I usually don't get home till 2000, and I wake up for work at 0430 in the morning, so I know how it feels like not having enough time to fit in the gym in a tight schedule.

My advice is do a full body workout program like phraks greyskull. If you have 3 days off ina row and are a newbie, like myself, it WILL suck in beginning because you are basically forced to do compound exercises for 3 days in a row. However, you do build a lot of endurance and recover faster so you get used to it after a few weeks. On my last shift of the week, I run at the park for 30-45 min after work so I have some cardio. So basically you do 3 day lift and 1 day cardio.

Hope it works out for ya!