R class ( w251) gearbox

[andyp144]

I run a 2007 R class 320 cdi 4matic and an odd thing happened just now. I pulled out of a junction and the car just didn't do anything, revved like the clappers but very little forward motion, crawled up the road, pulled off, selected D, nothing,selected R , nothing, switched off, switched back on everything o.k. This hasn't happened before and no warning lights came up. Anybody got any ideas. Thanks.