When you say at night, is this in particular when you lay down, especially on your left side?
When I lay down or even when it is time to sit and "relax" at night.
I don't have much knowledge with this condition, perhaps others will come to your aid, I hope so. About a week after I had my 5 stents inserted, I suffered this and it did scare me until I realised what it was. I panicked the first time because I suffered a bad episode of arrythmia after my procedure and I thought it was happening again. Mine too came on late in the day, any time from 6pm onwards and lasted ages. The only way I managed to stop them was to have a sleep. Strange thing is, they stopped after a couple of weeks, they vanished as suddenly as they started. I only had one a day and I really have sympothy for those who suffer with it. I even thought I had trapped wind and forced myself to burp several times but this had no effect. Coughing, jumping up and down, running on the spot, holding my breath for a minute, nothing I tried stopped the flamin thing, only sleep. Why a short nap of 30-60 minutes would stop it I don't know.