I think the best business ideas come from someone's own personal frustrations. If you have a problem with something, then there are likely hundreds, thousands or millions of people struggling with the same thing. Many times these ideas can seem somewhat trivial, but the fact is that a problem is a problem.......and often needs a solution.
I struggled with sweating for pretty much my entire life. I remember in elementary school seemingly being way more sweaty than other people when I played sports. I realized that I was sweatier than other people when I was at school dances. I realized I was just a sweatier dude than other people in pretty much ANY situation. There are worse issues in the world, but it was an embarrassing problem for me and something I was super self conscious about.
I have probably hundreds of stories of me sweating at bad times. Vegas club.....Yes. School tests.....Yes. At a dinner table with strangers.....Yes. Important job interviews....Yes. Cocktail parties talking with important people.....Yes. I would have techniques to try not to sweat that were always really crude, but always on my mind because I just HATED SWEATING.
I would bring towels to dance parties when I was a kid. Yes....I had a towel in my hand in 7th grade at school dances. I'm sure the girls thought I was a stud. Later in life I would leave situations when I could even get a hint of myself starting to perspire and run to the bathroom to put cold water on my wrists to help cool me down. I'd just leave a dinner or party or discussion for 15 minutes while I tried to cool myself down.
Throughout all these experiences I struggled with my undershirt. I HAD to wear one because if i didn't my sweat would go right to my outer shirt. Since I would sweat so easily that could happen in an instant. The white cotton undershirt would at least absorb some sweat and give me some time to figure out how to cool down. The issue was that the cotton undershirt was thick and served as an extra layer for my potentially steaming hot body. It made me HOTTER.....when I needed to stay as cool as possible.
You can see where I am going with this. Figuring out how to make an undershirt keep me cooler would alleviate a lot of stress for me. I could stay in conversations longer. I could go on dance floors more confidently. I could walk outside in a warmer day not worried about how quickly I would start sweating. I could not sweat in job interviews. It could actually be life changing!
Now the question is what issue(s) do you have that aren't adequately solved? Can you see other people appreciating a solution? This is how ideas start. There are many successful startups that began this way. Spanx. Warby Parker. Bonobos. Uber. Kate Spade. Kendra Scott. Rent the Runway. Method. They started as a problem that needed a solution.