Bubbling usually occurs directly after installation of flooring. Five years later sounds suspect.
I will assume that this is a sheet of flooring not squares. Correct. I am going by your statment of pulling back......
Is this actual lino or vinyl?
Before you pull this up and before you consult a flooring professional, just try this for grins. Get a bag of ice and make sure its not punctured. Then lay this bag of ice over the bubbles. Let it stand as long as their is ice. Then see what has happened. I have seen this work before.
Have you had any water leaks in the area of the front hall? Do you have any stress cracks in the walls or headers around this area that are new? Have you had a dry or very wet period of time in the last 2 months?
I am very confused about bubbles this late in the life of the floor. Something has to be happening below to have this happen five years later.