What is with the heck of me?

Spring Fever:

In the northern hemisphere the symptoms usually arise from mid-March to mid-April, and depending on the person may be more or less pronounced. Weariness (despite an adequate amount of sleep), sensitivity to changes in the weather, dizziness, irritability, headaches, and sometimes aching joints and a lack of drive are the most common.

(wikipedia)

So now I know what's wrong with me. Spring fever.

.....not to be confused with cabin fever....which I've also been known to come down with....occasionally.