Power supply higher voltage on startup
That's called a voltage surge.

As always, the truth is the datasheet. In this case, in the Absolute Maximum Ratings section:



Apparently, your LED strip can withstand voltage surges of 7V. Although it seems OK, you'll be already on the limit each time a surge happens and that can be dangerous.

So you might want to consider using either:


A better power supply with no surges, or
A transient voltage suppressor (TVS, aka tranZorbs).