Turn Signal Flasher Unit problems of the 2002 GMC Envoy

All these problems come and go, somtimes depending on the outside temperature. Some of it got fixed and came back again. The major problems are that the vehicle shuts down without any warning - no engine no electric nothing-, so its even not possible to call on star! the other thing is that the transmission start to shift gears while driving on a leveled raod at consistant speed. All this items got fixed and come back after a while. Dt.