aircraft engines can always be tempremental to start. As has been said above, the starting system is nothing like car starters which we are all used to starting 1st time with no problems.
At my school, there's a arrow that is a real bugger to get going. It seems that only one instructor has the touch sometimes. I've seen other experienced instructors trying for up to 3 hours (trying, then giving it a rest and trying again) with no sucess, then this guy goes out and starts it 1st time.
Sometimes its just knowing what your specific aircraft needs to get started. treat her like a lady!