Most guinea pigs love human attention, but some can be more nervous - especially newcomers. They’ll need to get used to you first.
If your guinea pig squeals when you pick them up, the first thing to do is to make sure you’re not holding too tightly. Once you're sure your grip is correct, give the guinea pig a thorough health check. Any squealing or visible discomfort when being handled can mean your guinea pig has a medical problem, such as mange.
Some guinea pigs can be a little timid at first
If your guinea pig appears to be in good health, the squeal may simply have been one of fright. There are various ways of helping your guinea pigs get used to you. Try hand-feeding them through the bars of their run, so that they can get used to the presence of a giant human hand. Spend lots of time around them, so that they come to recognize your scent and lose their fear of your presence.
If you have other pets, the guinea pigs may be reacting to their smell. As far as the GP is concerned, the scent of cats and dogs is the scent of predators! Keep the other pets well away, and wear clean clothes that don't have the cat or dog smell on them. Wash your hands thoroughly too, for the same reason.
Over time, show the guinea pigs that you are both harmless and great fun to be around! Reinforce the idea by arming yourself with some tasty treats for the GPs to nibble on.