Question: What are likely causes of a temporarily reduced urine flow rate?

What are likely causes of a temporarily reduced urine flow rate?

62 year old white male. In good health. 5′ 10″ (1.77m) tall & 172lbs (78kg).

For approx 4 days urine flow rate was noticeably reduced (maybe by 50%). Overall the volume didn’t appear to be affected (just took longer to pass). There was a slight burning sensation (inside the end of my penis) as passed urine. Urine was not cloudy.

I’ve had cystitis before, many years ago (caught from my wife). It didn’t seem like cystitis as was not like passing razor blades and didn’t have urge to go very frequently (and from what I recall the flow rate wasn’t affected then anyhow).