If you have ruled out that this behavior is due to some type of illness, it is normal that at the beginning it is a bit shy and scary. They have to adapt to everything around them, you and your new home. Keep in mind that guinea pigs are animals of prey, so when they are scared their innate reaction is to hide and remain still. Try to gain your trust by first reaching your hand so that it smells you, then always take it from the front so that you see your hand approach and do not panic so much and put it in your lap. Give caresses and the food you like while you have it. The first time may not last more than 1 or 2 minutes, but you will see how as the days go by each time it will matter less to be with you. They almost always warn when they want you to return them to their cage, either with a snap of teeth, small bites, etc. Soon he will get used to you and will even “call you” when he sees you pass by to pay attention or give him food.