Yes. The saying in physics is, "whatever is possible is compulsory".
From a quantum field theory point of view, the fluctuations constitute the vacuum. They are the vacuum.
Can this requirement be labeled "a cause" of the fluctuations?
No.
I have heard it said that if physical laws do not prohibit an event, it will occur, eventually. For example, based on quantum probabilities, it is possible to compute the probability of a beer can spontaneously falling off the table to floor. The answer involves some huge number of zeros, but the possibility is there. Does this "potential to fall" constitute a cause?
Quantum fluctuations don't involve sudden, unconserved changes in momentum that would be necessary to fling a beer from a table. Energy and momentum are conserved. So instead of the beer, I'll use an example of neutron decay. Does the potential to decay constitute a cause? Not in any meaningful sense, I'd say.