The Norfolk Coastal Path is one of the best walks for its scenery and wildlife and its infrastructure. 'Infrastructure?'
Yes, it's an easy route to walk in sections now and then. Or, you can walk its whole length without having to worry too much about where to park. It's easy to get back to your car (if you drive there) or find somewhere to stay.
There's a regular bus service between King's Lynn and Cromer. It runs hourly (mainly) throughout the day. In other words, you can park your car at a point along the route. Get onto the path and head off to a bus stop in one of the villages along the way. If you get tired, you can always cut inland sooner on one of the many paths off it.