First rule of working out is don't put yourself in a position that you will hurt yourself. This is a smart approach. You can go easy on the weights at first, but make sure you lift with a purpose. Too often we think just going into a workout and lifting some weights will always do good. It doesn't. Do your set with an intensity that you would if you were lifting heavily. Also, make sure you increase your weight...even if it is by five pounds...every week. A strength program won't do you any good if it isn't progressive.
I sit at a desk all day too. Look into a standing conversion desk if it is affordable. It will allow you to stand and then sit. The purpose isn't to stand all day, but to shift from standing to sitting several times throughout the day. There is research to suggest that standing desks improve blood pressure, help burn more calories, and improve mental focus. Seriously...I have one and it is kind of a life changer for me.