Warmup:

5 minute shadow boxing/skipping (or virtual skipping if you have no rope).

Workout: 

Beginner: (100 reps)

20 Push-Ups (4 sets of 5)

20 Air Squats (2 sets of 10)

20 Chair Dips (4 sets of 5)

20 Sit-Ups (2 sets of 10)

20 Back Extensions (2 sets of 10)

Notes:

The key here is to perform the circuit with as little rest as possible and to master each exercise with good and safe technique i.e. don't cheat the move.  For example aim to do a full press-up rather than use the knees.  

Sometimes we dismiss exercises such as the above because of their simplicity.  But sometimes a back-to-basics approach works.  This will work multiple muscle groups at once (compound work), ensure a full body workout and improve coordination with its integrated movement.  You will also find a cardiovascular element with your heart and lungs working hard to supply blood and oxygen to the working muscles.

Also don't take too long to complete.  These should take up to 15 minutes maximum.  But your goal is to complete this in less than 7 minutes.  If any of the circuits take longer than 15 minutes.  Be patient, you will improve.

Let me know how you get on!