I have A 2003 E250 The temp gauge goes up then down then goes back up and pegs turn key off couple time goes to normal and then have heat.Changed water pump ,Thermostat flushed and bled air.Going Crazy

 

A good place to start would be to check all ground connections you can find.
Then look for any wiring that may come from the temp sensor that might be rubbing against any sharp edges . There could be a rubbed through spot that is causing an intermittent connection. Any good diagnosis starts with a good visual inspection.
Does this vehicle have automatic climate control ?