When squatting try to keep your lumbar (lower back) as neutral as possible.
Take a look at the two comparisons, in the left clip where I have gone for the most depth you can see at the bottom of the movement the posterior tilt (tailbone tucks under). This could be due to limitations in my mobility and tightness through my hips- in which case creates flexion in my lumbar spine, placing load through the lower spine like this is a very common cause for injuries! ..
It is unavoidable because for “ass to grass” squatting ability you need to have both great ankle & hip mobility.
Instead & to eliminate the shift and to spare your lower back you need to sacrifice the depth shortening the ROM as I have done in the right clip- this will also ensure you keep the tension on the working muscles. ..
Squatting isn’t for everyone, & if you find it technically difficult to execute there are other alternative exercises you can do.. try working on uni-lateral movements- I.e. split squats, box step ups. (I will demo these in another post for you guys). Also look to include plenty of mobility work/exercises too.