1. managing vacation time.
2. it can take a toll on your back when working under the hood or installing heavy parts without any assistance
3. depending upon the type of dealership you are working at, luxury car vs non luxury car, to speed up the time to fix and working on as many cars as possible
4. working conditions and temperatures ( summer vs winter), inside in temperature controlled environment vs non temperature environments
I hope this helps. This is all part of the nature of the job , but it can be a fun job if you enjoy working with your hands and solving problems.
I think if you like it you may not find many difficulties, but maybe you will find the next:
-Problems about electrics systems
-Problems with the desing of the car
-Problems with building the fixes
-Problems with the size of the car, and how to access to some autoparts
But as many issues you fix the more easy will be fixing them