My 749s has a history of starting problems. The batteries do not hold charge very well, especially if there is an alarm on the bike. It could well be that your's is not really fully charged so it is just on the verge and gets enough from the engine running to keep it there.
When we had a new garage put up last summer our bikes were in temporary storage in a neighbours stable. With no convenient power point I did not put Optimate on as I would normally. 4 weeks later the monster was fine (no alarm) but my 749s was totally flat. I could not even deactivate the alarm when I inadvertantly set off the motion sensor and we had to just wait for it to stop - much to the annoyance of the residents in the other stables! Battery had to be charged before I could move it.
Just my 4-pennth worth ... long winded as usual