icemilkcoffee 

I just bought a used bike with Shimano 105 5700 2X10 components. The right shifter doesn't seem to have any distinct click for when you try to shift one cog. Sometimes I try to shift one cog and end up shifting two cogs. Other times I thought I shifted one cog and it turns out I haven't shifted at all. Should there be a distinct click for this shifter? The left shifter is similarly vague for the trim shift. When I am off the bike and standing still, I can hear an audible click when I push in to trim. But the click is so subtle that I absolutely cannot hear or feel it when I am actually pedaling along. Is this normal?
This is the first bike I've owned which has these STI brifters. My previous bike was a recreational bike with twist grip shifters. With that bike you could always hear, feel and see each shift. Whereas with this new bike I feel like I've gone back to the friction shift olden days.

Leinster

My 5700 shifter does have a very light but audible and feel-able (if that's a word) click when going to a larger cog at the rear. You probably wouldn't hear it in traffic/on the road.

Shimano are known for having a very light feel to the shifting; my Campagnolo shifters on other bikes have a distinct clunk sound when shifting in either direction, but at the same time it takes a bit more finger-force to make the shift.

icemilkcoffee 

That’s my issue! But I can’t even feel the click neither. Is it because the shifter is worn out, or is it always that vague?

KJK

I'd try this:

Leinster

I wouldn’t call it vague. It’s a lighter touch than my old 9spd shifters, but I’ve never had a trouble of not knowing if I’ve shifted or not.

bruce19

I have bikes with 105 and SRAM Red. To me the difference in feel and sound is like an auto vs standard transmission in cars.

dsaul

Welcome to Shimano's "light action shifting". I hated it and would rather use Microshift with their loud audible clicks.