Firstly Start slowly and build up gradually. Give yourself plenty of time to warm up and cool down with easy walking or gentle stretching.
Secondly Break things up if you have to. Exercising in short sessions a few times a day may fit into your schedule better than a single 30-minute session.
Thirdly Listen to your body. If you feel pain, shortness of breath, dizziness or nausea, take a break. You may be pu-ng yourself too hard