07 es 350. Ml nav system touch screen don't have problems with radio nav heat or air or phone but the touch screen sometime work when touched. First time driving no problem but 20 -30 min touch stop working but everything g is on and working

 

Sounds like your digitizer might be going, there's probably no fix for that but to replace the entire unit.
Good time to start looking for an aftermarket unit.

 

I think that there are digitisers available on Ali for that car.