If my Twitter timeline is anything to go by this is a very common problem.
Usually I wake up with cramps or spasms. Increasingly it is a failure to regulate temperature.
Sometimes it is the cat and his insistence of supplying a (loud) monologue of his nighttime activity.
Today it is the rare (and this is why it is rare) double meds dose. I kept the rule and took the 2nd dose before midday but it makes no odds.
Classic 'old lady who swallowed the fly'... or as The Verve put it; "Now the drugs don't work / They just make you worse".