Numbness & weakness every time I walk

This is a new one for me. Every time I try and walk somewhere I get numbness and weakness in both my legs after about 5 minutes. I thought it was just a one-off last week... but I've now tried going out twice more and exactly the same thing happened. Shortly after the numbness, I get pain in my hip and ankle with each step I take. It's really limiting my mobility and making life difficult. Has anyone else experienced anything like this?
Edinburgh, Scotland, United Kingdom