Just started using SPD's, done about 10hrs over the past week or so.

While I'm riding I get numb toes. They are also going numb hours after cycling, when I'm sitting down relaxing in the evening.

Any ideas? Is it just the way of SPD's or could I have set them up wrong?

More likely your shoes are too tight?

what he said. bad circulation! loosen them or wear thinner socks

what sort of riding have you been doing with them and what shoes are you using? For big road milage, the combination of small contact and flexible soles isn't great. However, it could be as simple as doing the shoes up too tight or needing to move the cleat back a bit (moving the foot forward). Road rides like ball of the foot over the pedal spindle but for off road, your fott can go a little forward of this without the world ending. It could also be a varus or valgus tilt issue and your foot doesn't like being clamped flat. Or perhaps a metatarsal button would help things.

Shoe tightness could well be the issues.

As I'm not used to SPD's I've pulled the laces way tight with the aim of having very positive twist to get my feet out confidently. I'll slack them off on my next ride, tomorrow.

Cheers.

What shoes? I've just started with SPDs and find the Spech Tahoe/Crank bros Candy setup very comfy

check your arches, if you have a high arch and no arch support in your cycling shoe, then you will compressing your arch flat, which can lead to numb toes, pins and needles etc. Leave a footprint with a wet foot on a piece of paper to check. Try Spec shoes as they have more support as std than most, you may need an insole with more arch support, Spec also make these in three heights.

mine was definatley shoe tightness when i used to get it, did the velcro up way too tight.

Tight shoes, or the typw of shoes you've bought just don't suit you.