I also remember my grandma telling me when I was young that you could "pray" to the "animas" (which are recently passed people that hang around) to help you wake up at a certain time and it would happen.
		
		
	 
I loved it about your grandmother.

 It would be great if many more people would listen to their grandparents, because they know a lot about things that actually work!
I too have this thing about waking up a little before the alarm clock goes off. In my case it is exactly what Joe said:
	
		
	
	
		
		
			Basically, when I set the alarm, I'm doing more than just setting the alarm, I'm also consciously setting an intention to wake up at that time the next morning, and maybe thinking about it being important to do so.
		
		
	 
Also this:
	
		
	
	
		
		
			It's a bit weird (or maybe impressive) that it would always do it before the alarm goes off though, which has always been the case.
		
		
	 
At some point I have thought that this might have to do with something that has been mentioned here as "remembering the future".
 However, now I have another way of reasoning it out or imagining why the phenomenon occurs.
If my reasoning were to be correct, it would apply to both cases. That is, both for why we wake up before the alarm clock we set ourselves at a certain time, or for the cases where there is no pre-established time, as in the examples of Gaby, who also wakes up before the alarm rings or a call to attend an emergency, or whatever it is that requires her attention.
The idea I get, is that that part of our consciousness that is not sleeping while our physical bodies are, does not stop reading the information field at any time.
In turn, that part of our consciousness to which I refer, is not the one that is limited by the perception of linear time. Not even when we are in vigil. If we rarely pay attention to it when we are awake 

, or if we generally do not notice it except on occasion, that is another matter.
What is certain is that this consciousness is there and is part of us at all times.
Then, taking into account how inconvenient it is for our health the abrupt changes in our different rhythms or brain frequencies while we sleep, that the appropriate thing is that these changes of rhythms in the brain are natural, harmonious passages and, that includes that for the moment of waking up naturally and in a healthy way, there is some specific frequency, one that is the most appropriate for that moment, then, we will always prefer to wake up in that way and not by the sudden sound of an alarm.
Therefore, if we give enough importance to wake up at a certain time, even if we have an alarm clock we set it to make sure, it is very likely that that part of our consciousness that I mentioned before, through its resources, will help us to wake up respecting the natural rhythms, as close as possible to the time we set the alarm clock and always before it rings.
If we value and take advantage of this great opportunity or not, because the temptation is to stay in bed, risking to fall asleep again until the alarm goes off, which is paying dearly for a little bit of pleasure, that depends on our decisions while awake, in relation to our willpower. 
I think that in the same way, this part of our consciousness helps us to wake up before the alarm, phone or whatever rings, to attend emergencies for example, where there is no pre-established time. 
I think the way it does this has to do with what was said before.
This part of our consciousness is not conditioned or limited by linear time.
And it is always reading the information field. Rather, the part of the information field to which it has access.
Within what it can access from the information field, it is quite possible that there are all the events where it is linked in some way.
I will give a practical example:
Suppose that in some house during the night, a child is running a fever and the parents are desperately asking for medical assistance by phone.
At the nearest hospital, it's Gaby on duty 

. She is sleeping while she can.
From our perspective, at issue at about few minute someone will wake up a Gaby, for example with an alarm, to go and attend to that emergency.
The part of her consciousness that is not sleeping, the one that is reading the information that is linked to her, and the child's event is, knows perfectly well that this alarm will sound abruptly to wake up the sleeping part of her. 
Then she can act in some way, so that her sleeping part wakes up in a healthier way, before the sound of the alarm.
It can do so, because let us remember that for that part of our consciousness, the laws or constraints of linear time do not exist.
If what I am saying makes sense, much of what happens to us in the form of precognition, presentiment, things of that kind when we are in vigil, may apply the same dynamic.
  
That is, a certain level of our consciousness that is registering information that has some link with us, and that reading is in the present continuous.
That's more or less how I imagine it could be.
Translated with DeepL.com (free version)