To get into a study habit you need to devote a time and place daily for it. If you've blocked of time in your calender for studying and are avoiding it. Then your problem is prcastionation. And the Get Around To It paraliminal may be your fastest track to getting started.
Look at your ultimate goal. Why have you taken up studying again, What was your purpose?. Write it down and put it somewhere you are reminded of it daily.
Every time you sit down to study have a plan what you want to know when you have finished. Give yourself reasonable time to study what you have to and if you finish early... finish early. Even one 30 minute study session a day is better than none.
Make your target the minimum passing grade and anything better than that is a bonus. If you find the upcoming exams daunting you might want to see if you can get copies of the previous years exams. They will give you some insight into what is required of you for the exam and a realistic idea of what is expected of you.
Good luck
Alex