This part does a nearly 100% rebuild of the valve you have
https://www.homedepot.com/p/Korky-Replacement-Cap-Assembly-for-Fill-Valve-R528CM/202666007 and here are the instructions
https://www.korky.com/sites/default/files/media/product/pdf/R528_1.pdf No tools required, should take you less than 10-minutes, and less the second time. Korky makes many (not all) of the fill valves for Toto toilets sold in the USA. From the shape of the top of yours, it is almost certainly one of those. If you follow the instructions, you should see the cap I'm talking about. If you don't, you might have something different, but that's unlikely. I like to have one of these caps available so I can just swap it when I notice a problem rather than having to run to the store for one, or wait for one to be delivered if I order it online. Here's a video showing how to replace it...
It does wear out. The higher your water pressure is, and the more water treatment chemicals in your supply, the faster it wears out. In 99% of the cases with this valve, this part fixes your problem. If you take the old one out, and look at the underside, if it's not a smooth shape, or is cracked, it is the culprit. With excessive water pressure, the seal gets formed to the part above it and eventually cracks. In the interim, I've found that it can have a delay after flushing before the thing breaks loose so water can flow. With the water I have, I find mine last maybe 2-3 years. With some people, theirs can last a decade or longer...it all depends on the water pressure and chemicals in your water.
If your water pressure is excessive, you need to address that, as not only will the toilet valves exhibit issues over time, other things will, too.
Note, it's not uncommon for the water pressure to rise overnight when fewer people are using it, and they're pumping water up into the water towers for the next day.