Over methylation: If your folate is higher than body can adjust to, you might feel palpitations, restlessness, breathlessness, histamine reactions. If you're on a path to increase your methylation by slowly increasing these supps, you'll probably run into this.
For the palpitations, potassium. For the possibly unpleasant speediness or other things I mentioned, there are 2 approaches. Ben Lynch suggests dampening everything down by taking B3. I, OTOH, always had good results by immediately taking a 1mg sublingual B12, an essential partner in methylation.
Methyl trap is temporary low folate. These symptoms will typically involve skin...acne, angular chelitis, others.
It's an ongoing delicate balance between B12 and folate.
sheclimber has created a new 9 page guide to methylation, linked in my signature. Pages 5 and 6 address your question. It's in a list/table format.