While l am driving,temp gauge drops to low abruptly.Tranny shifts a little harder and engine runs a little rougher while it is low.If l turn the car off while needle is down,it wo not start(turns but no start).If l wait for it to return to normal( happens in seconds to maybe a minute) there is no problem to start it.If l turn it off with needle in low,l let the switch in ''on'' position until temp needle goes back to normal and then starts normally.This happens very often.Any help? Anyone with the same problem?

Sounds like more than one thing going on. Get the battery terminal checked out and then get the transmission and get a new car check on it, they will find out whats wrong.