2002 Honda Odyssey will only drive between 20 and 40 mph...

My 2002 Odyssey started to break on its
own after going past 60 mph, it would break
on and off until it came to a complete stop
and I then would need to turn it off and
back on in order to move again. I then drove
it on a 3 hour trip to Vegas and had no
problems the entire ride until about 1 hour
away from home. But the problem got even
worse because it was now doing it after
passing the 40mph mark.