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PortPlugs - USB C Silicone Dust Plugs (10 Sets), Compatible Samsung s8, s9, Note 9, Pixel, One Plus, Any Type C with Headset Jack (Black) [link]
Just search for "USB c port plug" and you will find a ton. I have a set to cover the ports on my laptops and tablets.
PortPlugs Anti Dust Plugs USB C (10 Pairs) Compatible with Samsung s10, s9, s8 Plus, Note 9, Pixel, Any Type C, Includes Headset Plugs and Cleaning Brush (Black) [link]
Here is the link for the ones I use. They're cheap, but they fit in the holes perfectly and for the past two years I've never had a problem with dust in the charging port.
It's cheap, comes with a bunch of them, and a little brush to help clean your porthole. Or buy anything like it. I do recommend getting one with the brush though. I keep the brush in my little ifixit tools case in my computer drawer.
Probably clean your charging port. I get that issue rarely.
You can buy these. They are little plugs that protect and keep dirt and shit out of your port. It also comes with a little brush. I like to turn odd my phone and dab the brush in a bit of rubbing alcohol. Then brush around the inside of the port, also trying to do a scooping motion to pull out any gunk. Then let it dry of course before turning it on or using a charger. Make sure you have a wireless charger because sometimes the moisture detected thing pops up for a few hours after but it goes away quickly. That's fixed it for me every time.