First, you can clean bearings and anchor of motor. You can first try externally when you remove platter and spray either DEOXIT F5 or CRC lube over and rotate the spindle back-fourth while doing that. After few hours turn it on and see what's going on. If did not help, you should clean motor internally including all possible bearings as well. Clean magnets as well.
If internal cleaning didn't help, the problem may be in electronic motor board where most of caps and transistors should be checked/replaced when needed.
If internal cleaning didn't help, the problem may be in electronic motor board where most of caps and transistors should be checked/replaced when needed.