>The funny thing is that, if I let myself sleep for a few minutes (5-15)
You're essentially taking a nap and waking up before entering deep sleep. This is the refreshing kind of nap. Conversely sleeping just a few minutes more and waking up in the middle of deep sleep would make you feel grumpy and tired. There are some polyphasic sleep techniques that basically exploit this and have sveral short naps of light sleep throughout the 24 day instead of a night's sleep.
You're essentially taking a nap and waking up before entering deep sleep. This is the refreshing kind of nap. Conversely sleeping just a few minutes more and waking up in the middle of deep sleep would make you feel grumpy and tired. There are some polyphasic sleep techniques that basically exploit this and have sveral short naps of light sleep throughout the 24 day instead of a night's sleep.