Is Mom trembling because of meds?

Mom is 93.5 years old, 5'3", and 109 pounds. She takes 500mg Acetaminophen and 300mg Gabepentin 4 times daily, 50mg Tramadol 3 times daily and 500mg Methocarbamol once daily for severe arthritis pain, plus 325mg Hydrocodone as needed for the same. She also takes 15mg of Mirtazapine at bedtime for sleep, 500mg of Medformin for diabetes, 5mg of M-Lodipine and 50mg of Laspiring, and 50mg Metoprolol for high blood pressure, 81mg asprin, plus a few vitamins and minerals.

Every once in a while, she will shake for 15 seconds to a minute. This started when she began to take the meds for arthritis, but none of them list trembling as a side effect. Or they do, and somehow I missed it.

Is this normal? I will put an ask into her Doctor but it can take a couple days to get a reply. She's not in distress, just curious as to what you have to say.

Thanks!