When you were born, they were only married for a few years, which is the running-in period after marriage. The contradiction between mother-in-law and daughter-in-law is the most difficult contradiction in the world. Just after giving birth to you, your mother is prone to temporary depression such as postpartum depression. These factors add up, and quarreling is normal.
There is nothing to worry about.
I know that the years after the old marriage were the most difficult running-in period. Husband and wife survive through love, which is followed by a hundred years of harmony and a long life together.