Kenmore series 70 electric dryer - runs for about 20 minutes and then stops - timer knob stops moving after the 20 minutes. Anyone have a similar problem? Or a suggestion?

My guess is that it is getting too hot and shutting off for safety.

I would pull it out from the wall and clean the exhaust hose (and everything else you can reach) of lint. Also, clean out the hose that goes inside the wall -- all the way to the outside.

That will most likely fix the problem. If not, then you may have a worn-out thermal limit switch, or some other component like that.

Hope this helps,
WallyH