Suddenly felt incredibly sleepy in the middle of the day, concerning?

About 20 minutes ago i was just taking a break from work, was sitting for a while so that couldnt have been the trigger. But i suddenly felt some form of upcoming tiredness that worsened within seconds and i had to fight to stay awake. My vision also blurred a bit. After a minute or two i could move properly again but i still feel exhausted. My breathing is normal and vision as well. Im slowly feeling better but i can feel my pulse in the left side of my neck. If i feel the muscles there theyre tighter than normal, only on that side. This has happened a few times before but lighter and at night, so i didnt think too much of it. Now its getting worse though and cant be linked to tiredness, so im getting a bit worried. I dont understand where this came from and am unsure whether this is something that needs medical attention? (Doctors here write it down if you come for stupid reasons, then dont take you seriously after. Hence why i hesitate.) Im 21 years old, i slept well, no known vitamin deficiencies and a pretty good immune system. No fever either and my stress was low. Im genuinely confused why this happened and hope someone here would maybe know?