overheating and stumbling

Nissan370

on my way home and noticed the car was idling high and stumbling some.

looked up at my oil temp and it was sitting around 230-240 high for the temps being only 40 deg.
i pull over and also notice my engine temp gauge is jumpping from cold to normal temp then back and forth again. some times just sitting on low as if the car is not warmed up.

i pop the hood and remove the coolant reserve cap slowly and its boiling.

i turn the car off let it set for a few and i walk to get some oil and coolant
may not have needed the oil but i used them both.

got home. and i am strongly thinking my thermastat is sticking.

any help thxs

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370z vsr motorsports single turbo/built motor 9.1cr 525rwhp/450rwtq @ 10.5psi (stock maf maxed out)