Being a distilled spirit, scotch tends to be pretty stable once it's in the bottle, if anything it would be exposure to air that could impact the flavors, but as long as the cap/cork is on tight you should be OK.

As Jojo mentions, this is more likely a result of your palate because you mentioned you are new to scotch. When you are new to a particular spirit, it may take some time for you to notice various subtleties that you would not have picked up on at first.

Gaining an experienced palate in regards to whisky or other spirits is often a good thing, since it can allow you to more fully appreciate the craft of making a particular spirit, or recognize some very subtle flavors you were searching for based on tasting notes. But for someone new to scotch, those distinctions can be much more difficult.

The flip side is that as you gain experience in tasting whisky, you will come to find that you don't like some brands as much as you initially did because you began to pick up on flavor characteristics that you don't find as pleasant. This can be unfortunate, and it can also become quite costly as you begin to move up the price ladder to find a whisky that better fits your rapidly sensitizing palate!

Good luck, it may be a bit pricey, but it's fun