I've found that a couple of my hard-starting pens were due to 'baby's-bottom' problem, where the nib has been over-smoothed so that a small gap is present where the tines should be flat with the paper. Due to the surface tension of the ink, this leads to them not starting on the first stroke. You can usually see it through a loupe.
Weirdly this seems to happen more often on more expensive pens - a Visconti I tried, an Omas I tried and my Parker Sonnet all had these issues. The Sonnet ended up needed minor adjustment by someone more experienced than me.
Of course, it can also be due to a lack of ink flow, but I've found that if it still occurs whilst fully inked, it's likely to be a nib problem. Just one of those idiosyncrasies which make FPs fun...
Yes indeed-nib flaws can cause all sorts of problems.
I've braved some work on inexpensive nibs and can usually straighten them out, but won't(for obvious reasons) work on more expensive nibs. Generally, I use fine grit sandpaper(2000 or higher) and "draw" figure 8s on it. If you do this while holding the pen as you normally would when writing, you have the advantage of the nib also somewhat breaking it in to your personal writing style. When doing any kind of abrasive nib work, however, it's ESSENTIAL that you do not place any pressure on the nib. Putting pressure on it can spread the tines and make a baby bottom worse or even introduce one where it didn't exist before.
Funny enough, I've mentioned and pictured here before my favorite, cheap Pelikan 105. When I first got the pen, it was a reluctant starter with poor ink flow although I trudged on with it. A few months after buying it, I had it clipped to the inside collar of my sweatshirt. I was outside walking one day and heard a faint "ping." I habitually reached up to feel for the pen, and only found the cap. Looking back found the pen, which of course had landed nib down and had one tine severely bent.
I'd already planned on ordering a replacement nib(it was $30 at the time, and on Pelikans the nib/feed assembly just unscrews from the pen body), but figured I had nothing to lose by trying to fix it myself. I went to my watch bench and carefully worked the nib back into shape then smoothed out the tip under magnification.
Much to my surprise, the repaired nib was FANTASTIC. It now starts easily, has a very forgiving sweet spot, flows well, and has just enough "spring" to give beautiful line width variation for someone like me who knows the nib well.
That was a VERY lucky accident, but also turned a $100 steel nib Pelikan into a wonderful pen. I don't suggest this course of action, and of course quit carrying pens that way
That reminds me that I need to send my Lamy 2000 back in for its second section repair. It lasted almost no time after the first repair. I'm probably either going to request a nib swap or a flow adjustment on this repair also, as I've been unhappy with the flow since the pen was new and would hope they could at least make it right on what is now a $200 pen(although I didn't pay that much). I could do it myself, but given my other experience it's hard to access the nib without at least inflicting some damage on the section(esp. since the entire feed is hidden, and one of the best ways to adjust flow is adjust nib-to-feed distance). One would think that they would have figured all of this out after 40+ years of making this pen. I also know that $200 is inexpensive compared to Mont Blanc and the like, but you still have to admit that it's not cheap for a pen.