So I want to use a Rotom-heat. I brought over a level 1 rotom heat from shield to shining pearl, but when I when to put Rotom Heat in Shining Pearl, it no longer had overheat. Could I have relearn overheat from the move reminder. Thanks in advance
No
Source
Serebii lists Overheat, Leaf Storm, and the like as Special Moves, which cannot be remembered via Move Relearner.
This person had the same problem as you and was met with the same answer as well. You can also find someone to trade the Rotom to to teach it Overheat before trading back.
Hope I could help!