Yes probably imbalanced discs, you could build a balancing jig and put a sticker on the top opposite the heavier side to try to compensate. I wouldn't continue playing them without that, will be hard on the drive bearing. If a balancing jig is too much work, you could randomly put stickers on, see how that impacts vibration, then remove and change position and amount of sticker(s).
Other option is rip them to an image or files, at the lowest speed supported, or find the files on the internet. Play from files or burn a new disc.