Different snakes act in different ways. My snake is usually quite active, and when he gets ready to shed he tends to Hide more. That's how I usually know. His skin will appear dull and off color, especially on the belly. Yes they sometimes refuse to eat as well, although my snake has eaten during sheds he has also refused to eat during sheds. The eyes get a "Glossy Blue" look to them eventually but this usually does not happen in the beginning. When the eyes get "That Look" you know the shed is soon.
Looking at your pic doesn't show much. The eyes look clear to me, but the skin does look dull. So (only a guess here) I'm going to say if your temps are correct, then your snake is probably getting ready to shed, but don't expect it overnight. The entire process can take 10 days to 5 weeks.
My snake actually refused food for almost a month during 1 shed cycle. Don't be alarmed, they can live a very long time with no food.