Rat seizure?

Hi, I am new to here and am just really wanting some advice, I have a female rat, I was stroking her and all of a sudden her body went stiff and she fell and didn't move at all for maybe a few seconds, this has only happened twice but I am worried it might be something serious, she doesn't seem to be in pain as she makes no noise at all, her body doesn't move so I don't think it's a fit but it's very sudden and she freezes up and will lay in the frozen position for maybe 10-15 seconds before being back normal like nothing happened
Does anyone know what this could be or what I should do

the next time she does it, can you pick her up and watch her nose and eyes? if there's a rhythmic twitch it still could be a seizure. I've also seen fear in rats produce this effect, albeit not often. How long have you had her?

Yeah I definitely will check, it's been 11 months I've had her and have only noticed it recently

How often has it happened. Twice in a day then nothing or ??

It happened once about three months ago and then again the other night so not very often but I noticed that it's when she wakes up suddenly, as the last time she woke up as I was putting their food in the cage and she started then I thought it could have been because she woke all suddenly