I'm a 62 year old software developer. My normal sleep is between 4 and 5 hours with occasional 6 hour sleep according to my Fitbit. Anything less than 4 and I f

I'm a 62 year old software developer. My normal sleep is between 4 and 5 hours with occasional 6 hour sleep according to my Fitbit. Anything less than 4 and I feel tired but I'm putting in a full days work with four or more hours sleep. In the past while driving long distances, if I started getting fatigued, pulling over to a Motorway services I could fall asleep for 20 minutes and that freshened me up enough to finish any journey.