If you are noticing behavior changes its time to seek a veterinary opinion. It could be old age, but it could some something that is treatable. Hedgehogs who are sick typically hide illness as long as they can. You may notice they don't run as often as they once did, then they may start to eat less, etc. its usually best to take them in just to rule out possibilities.
It could be old age, illness, or even arthritis is starting to creep up on him.