Random Fermentation

I brewed a Pumpkin Beer about a month ago used a good healthy yeast starter and everything in the primary fermentation went just fine as though it seemed. So I keep my beer in the primary for maybe a month as this is what I’ve been doing lately and skipping the secondary. I brewed this around 8/12 and just the last two days 9/17-9/18 it formed a whole new krausen and bubbling steadily. Is this normal? Has this happened to anyone else?

what was your OG & what is your SG right now?

I have actually had this happen in secondary. Transfer to carbon and it sits for a week and then starts a long slow fermentation, or so it seemed. No real change in gravity, bit foam and slow but steady bubbles.

Did not appear to be an infection.