I believe he just fell aslep, the grounding was at night. it is hard to understand what does a solo 76 year old sailor at thiis time of the year at night along the Portuguese shore when for the last night and today were forecasted strong winds.
Maybe he was just tryng to move the boat
to a safer place before the stormy weather
but even if the South West coast
has not many shelters he surely could have waited on Sines for better weather
and would be safe and have no need of sailing at night.