Van keeps shutting off on its own and overheating

You mean the engine, overheats then the engines stalls.?
that latter symptom is normal for overheating.

(some exceptions, ) my Corvette drops cylinders, 1 by 1 to stop
this.(but is still bad , if this happens)

does it overheat only stopped, only moving or both? (KEY question)

fix the over heat, cause. there are may ways to overheat.
from simple to comlex. and no web bunny on earth can guess it.
unseen.
ill list the simple:
1: low on coolant, no not the side tank, the actual rad is low,
check only on dead cold engine,below 125F (AZ temp)
2: bad RAD cap. not holding pressure.
3: wrong coolant mix or mixing 1 color coolant with another (bad)
4: water pump belt bad , or slipping or missing.
5: rad tubes clogged
6: fan dead,
7: RAD outside ofcore, blocked with filth.
8: blown head gasket,(or far worse)
9: bad water pump.
10: leaks anywhere, (this really is first)


one site that lists them all , every one,... is
http://www.fixkick.com/overheating.html