Clock Stopped at 3:33 When Father Passed

From my understanding of your question, The time 3:33 and the number 333 hold an emotional significance for you.

The number itself or, rather, the energy represented by the number 333, resonates with, among other things, humanitarianism and compassion.

It's a virtual certainty that because the number 333 holds an emotional significance for you, you will see it more often than other numbers. (The same would hold true for pretty much any number with emotional significance or personal meaning.)

A person sees many numbers during the course of a day. When a number with emotional significance or personal meaning is noticed, it tends to be remembered because of that significance. The other numbers generally aren't remembered. Why People See Certain Numbers All the Time talks about that.

When a person remembers seeing a certain number and does not remember seeing other numbers, it can seem to the person as if that particular number is being seen much more often than would be normal.

If you only wake up at 3:33, then I could only speculate why, because traditional numerology doesn't have reliable calculations to determine why that would be. If you also wake up at other times, you're likely to remember the 3:33 wake-ups with more clarity than the other wake-ups, again because of the emotional significance attached to 3:33.