It's been at least 25 years since I've taken Uniphyl myself, but I don't recall the side effects being any different than any of the other theophyline pill preparations ( ie, tremors, increased HR, that sort of thing). I do recall however, that theophyline medications were all the rage back then and people would occasional over-dose from taking too much of it.

Probably more important than dosage, is having your Theophylline blood level checked. I think a level of 3-5 is the preferred range for COPD nowadays.

I am on continuous oral MR Aminophylline (Phyllocontin 225mg BID). My level is usually around 12 mcg/ml blood.
My side effects are now mild, but still continuous-mild tremor, slight fluttering of the heart and nausea. If my level becomes too high (related to foods consumed, liver function etc) then I can become toxic very quickly: dizziness, vomiting, blinding migraine headache and I have in the past suffered seizures due to this drug. It needs to be closely monitored as an IV in hospital too.

It is best to avoid caffeine, cola, BBQ food & chocolate when you are getting used to your dose.

Even if your blood level is very low (under 7 mcg/ml (in the UK we measure it differently from in the US) the anti inflammatory properties of the drug are still beneficial, even if it is not acting as a constant bronchodilator.

It usually takes about 2 weeks for the dose to settle and your body to get used to the side effects. Good Luck!