Please take the time to read the very helpful green links, especially the guide about prey animal instincts and how to work around them. Guinea pigs are prey animals that in most cases (unless you rehome from a good welfare standard rescue) have not had anything in the way of friendly human interaction before they are thrust into a home and expected to work as instant animated cuddly toys.
This link her tells how things look from a guinea pig's view. You may find it a bit of an eye opener!
Arrival in a home from the perspective of pet shop guinea pigs
Unfortunately all the videos on social media are entirely driven by human interest and selection; they do not represent the reality - only what humans consider cute or funny. Who wants to see a piggy running away when you want to pick them up or cuddle them, as is pretty normal? When getting your information from social media, whether that is behaviour or illness, you always have to make provisos that they are never a proper representation of the reality. You either get what people want to see or, in the case of illness, all the horror stories and miracle cures but not the vast majority of perfectly unexciting recoveries that are not considered worth posting about.
Here is our hair cutting guide; the best way of dealing with a long-haired piggy that finds grooming stressful is to keep the hair on the short side, especially in the area that mat and soil quickest.
An Illustrated Guide to Hair Cutting