05 Mazda Tribute speedo not always working
 

I have a 05 Mazda Tribute, and when I got start it up and drive it my speedometer won't go over 20mph for about a mile and then will just start working. I've had someother problems and got them fixed and asked the mechanic to check the speedometer. Well the car was already "warmed up" so he didn't see a problem. Thought this was just a winter thing. I haven't driven it in a while and started to again and noticed that it keeps happening.

Anyone else have this problem or know of a solution? Any help appreciated.

Thanks