Paperback near-future novel in which there is an ice age coming, and rich people and politicians prepare an underground facility and go into cryogenic suspension for thousands of years. After they fall alseep, the protagonist and his team break in and take their place. They may have had mech battle suits.
I think you might be talking about Time of the Great Freeze (1964), by Robert Silverberg.
For centuries, men had lived miles beneath the ground in order to survive the great Ice Block that had submerged the earth. In an attempt to resume human contact, Jim Barnes, his father and several other daring men emerge from a subterranean New York to cross the frozen Atlantic. Coping bravely with problems of food and shelter, the fury of snowstorm and the attacks of wild beasts, and the strange, savage men who roam the Earth's ice crust, they finally reach London, only to find an angry and distrustful mob. Jim's pivotal role in establishing trust and unity is revealed in a suspenseful and thrilling climax.