This might seem like an obvious question, but how do you know when you're ready to try walking at normal speed?

I've been doing slow walking (in comfortable trainers with good cushioning) for several months. I'm now walking every day, and 2x or 3x on some days. Most of the time, my body still "wants" to go slow, so I'm still taking things very deliberately, but I don't know whether this is because I'm now used to going slow (sort of a chicken-or-the-egg scenario).

Does your body "let you know" that it's OK to start going faster, or do you have to push yourself a bit and see what happens? I guess I could try walking for 15 mins slowly and adding in a few minutes of normal walking here and there and gradually build up.