Hmmm I say flow issue still if its will climb to 210 then slowly come back,down.
Dumb question but did you check the fluid level? Take cap off when cold and check the let it get up to temp and see if you can see fluid movement thru the rad. Straight water or 50/50mix? Test your coolant maybe it's old and crappy. Drain and fill w straight water and retest. Also check you cap. Correct lbs of pressure? Sealing correctly? Beyond that if you see minimal flow throught the top of the rad maybe a new water pump as mentioned or there are clogged water passages in the block which would be worst case scenario after all else fails I'd say
Keep us posted....
