Skipping quarantine is a dangerous habit to be getting into this early in your snakekeeping experience. Even though you bought from a highly regarded person, I think Jimi would be the first to tell you that quarantine is just a smart thing to do no matter where you got your snake.

Sounds like you have some areas of concern with how you heat, control the heat and monitor the heat for this snake. Those need addressed quickly so the snake can be housed in the proper way it should be.

As far as "moods"......snakes, while not being able to do higher math, are quite able to take issue with something in their environment - sometimes that something is you. Sometimes it's about them being hungry, or their temps are off, or they are in shed, or interested in breeding and not in being hauled out by a human or stressed or heck, they just felt like it at that moment in time. In other words, snakes are snakes - they sometimes hiss, they sometimes strike, they sometimes are just laid back sweethearts.

Your job is simple really. Provide a proper environment for that specific snake appropriate to its species and size/age. Provide healthy food on a regular basis. Clean its home as needed. Handle in a manner that respects the snake. Pretty simple really.

If the snake is acting out of character, look to your husbandry first. If that's bang on then it's likely something else triggering the snake's need to strike. Eventually experience with that snake will tell you the most likely reason it's acting this way and whether to worry about it or not.