How come i wake up with sore feet, is this lack of exercise?

Depends: If the location of the pain is on the bottom of the foot you may have plantar fasciitis and this is usually usually worse first thing in the morning when you hit the floor.

Are they : Sore while in bed or on the first few steps out of bed? If the later sounds like planatar fascitiis, if the former that shoud not be the case and then we would need more info.

Pain after rest: This is a common symptom of plantar fasciatis. Other conditions can also cause this. I suggest you be evaluate by a podiatrist.