noticed temp gauge moving up like normal, and then falling back then to normal

What is your question?

thermostat opens, then idle increases to approx 1700-1800 rpm no miss,runs fine except for rpm. can bad coolant sensor cause this? like telling ecu temp is cold? no check engine light has done this constant for 2 weeks. sometimes it revs up and back to idle several times before settling at the 1700-1800 mark