I second the suggestion about hitting up your local bike shops: They usually let you do test rides so you can see if you like it before making a decision. They should also be able to guide you towards the right kind of bike.
On paper, a folding fatbike could fit the bill, but in practice, the folding feature can be kind of useless. A Tern Vektron is probably the closet quality bike I can think of but it's not really a mountain bike at all.