This is what the question says (emphasis mine):
a policy of automatically renewing subscriptions without any warning or notification that the subscription is up for renewal.
This means that you have already agreed that there will be an automatic renewal. There isn't anything shady going on that a renewal happens without you having known that would be the case.
Therefore, the emphasis is on the renewal itself, rather than the motivations of the company behind it.
Some companies do provide advance notice that something is about to be renewed. It gives you a chance to cancel your subscript if you wish. Without that advance notice, you can have forgotten about it and miss the chance to cancel (assuming you want to).
How could the quality of the this automatic renewal be expressed? It is abrupt:
1 a : characterized by or involving action or change without preparation or warning : sudden and unexpected
// came to an abrupt stop
// an abrupt turn
// an abrupt decision to retire
1 b : rudely or unceremoniously curt
// She has an abrupt manner.
// an abrupt reply
1 c : lacking smoothness or continuity
// an abrupt transition
A possible sentence used to describe the situation in the question is the following:
Without a friendly reminder ahead of time, we find your automatic renewals to be abrupt.
Anything that is abrupt has a negative connotation. As in the definition itself, it is sudden, unexpected, rude, curt, and lacking advance notice.