I can relate to this too. If I have nothing planned for the day, then I’ll keep sleeping past my alarm. But when I have something I need to wake up for, I am good about getting up. Maybe plan an important task for after your nap to help motivate yourself to wake up. Remind yourself how important it is while you’re falling asleep so it’s close to the last thing on your mind before it falls asleep. Also, multiple alarms five minutes apart so you don’t fall right back into rem so easily.

Another thing you may consider is to shorten your nap time from 20 minutes to 10 or 15 minutes. Everybody’s sleep is different, and you may be hitting rem by 20 minutes. You want to wake up before you get that far, so you may need to experiment with different times.