Could steroids make the heart flutter?

Not directly: The sensation of palpitations is fairly common and steroids (depending on the type, potency, and route of administration) have many possible adverse effects, including some cardiovascular ones. However, it is more likely that the underlying condition for which you are receiving the steroids, or associated conditions, may be the root cause of the "flutter". If persistent, talk to your doctor.

Yes : Steroids can promote arrythmias.