Not too much from starting, but as the story continues to progress I always get worried that story elements I introduce may not be well received, or that readers will not like that the story will / is progressively getting more serious the deeper the readers are pulled into the plot.
Also always have the feeling that 'I hope they enjoy it even though it looks like complete shit because I suck at drawing'
I'm also not good at sharing my comic especially with family and friends (been trying to get over this the last year, as you kind of need to advertise your comics to try and get readers.
EDIT: And I'm terrified of reviews, this is a thing that has persisted for years. I have never asked for them, ever. And when I get one from someone it takes a while for me to gather the courage enough to open it.