1998 coolant temp issues

[697498chevy]

Temp gauge goes past normal temp of 210 to 230 on every cold start . Been doing this a while . If I'm just tooling around town at 30 mph the gauge will max out and I get a check gauges warning . Temp always goes right down to 210 and is fine until another cold start . I've changed the thermostat and the temp sender located in the thermostat water neck . Also ran some flush thru the system and bled it . May change the bottom hose and try another rad cap . What am I missing ? THANKS !!