Energy to get to gym/workout

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Here's my problem...12hr night shift (1800-0600) posted in the ambulance until calls come out. Some nights are busy...some not. I'm having problems finding the energy to hit the gym after shift. I work 4 days straight one week and 3 the next. I struggle on my off days to keep my night schedule because my fiancé and family all work day shifts. I also cannot do pre-workout since I won't be able to sleep before duty. I've tried the get up earlier to hit the gym and it's even harder. Any fellow shift workers feel my pain and what do you do?!??