Can an arhat decide at any time to enter parinirvana?

One could think that yes, since an arhat had committed suicide by flying in the air and burning himself.

However, I remember that an arhat had to cut his throat to reach parinirvana. So this possibility to reach nirvana when he wants is not as “fluid” as one could believe, in the sense that some arhats do not have special powers to destroy the body in a snap.

An Arhat cannot commit a violent act towards themselves or towards anyone.

Parinibbana is entered by Highest Peace and Love.