No one here is qualified to give a diagnosis, only a vet can, and only from examining your cat and running any relevant tests, it would be madness to expect any kind of `diagnosis` for something like this on a forum.
I could easily say `sounds like Epilepsy to me` but it would`nt mean a thing, it would be words on a screen from a stranger and they could be completely the wrong words, same as `it could be a tumour` or `it could be [ insert any condition from a veterinary journal ]`.

What has your vet said - presumably with something like this you have taken your cat to be looked at ??

If not, why not

Sorry but there is no easy way to say it, nor should this be sugar coated anyway quite frankly :

you can`t continue to ignore whatever is wrong, it has clearly been going on for some time for you to give frequency measured in monthly occurrences, it could be so many things including life threatening, and you simply can`t get people on forums to give you a diagnosis, if you have`nt already, you must seek veterinary advice, not only because it`s morally negligent to do nothing through qualified channels but also failure to do so is a criminal offence under the Animal Welfare Act [ Pet Owners' Duty of Care ].

Please report back with what the vet says after you have been - you should be able to get a routine appointment within days at most, though if you have a good vets if you ring in the morning they will likely fit you in before the end of the day....