shaking after heart attacks

[TooManyBuzzards]

My father had two heart attacks, and stents fitted, a couple of months ago. He is gradually recovering and getting more good days than bad. However, on the bad days he wakes up shaking severely, so much so that he can’t hold a spoon to eat breakfast. Has anyone else experienced this? He takes asthma medication which gives him hand tremor but this shaking is a whole body thing