For the last 4 weeks i have been getting tired spells where all i want to do is put my head down on a desk and sleep. it comes and goes. coffee helps a little but not always. food doesn't help much. no change in sleeping or diet in last 3 months.

A few things: There are several causes for tired spells, these range from environmental factors (too warm a room) through to illness factors and include mood problems (like depression) and physical problems such as being overweight which can cause sleep apnoea. Have a look at this link https://www.healthnavigator.org.nz/health-a-z/t/tiredness-fatigue/ if you are still having problems then go see your GP.

Tired spells: Any new medications? Would consider evaluation for Lyme disease and also sleep apnea / narcolepsy testing. Check thyroid function , glucose ( for diabetes) as well as blood count ( anemia, white cell abnormalities), pulse ox and pulmonary function . F/u/ w/ doc

Many possibilities : Could be a medical disorder such a low iron(anaemia) or thyroid problem or something such as sleep apnoea or simply a post viral fatigue syndrome that may settle among others. Recommend seeing your GP for assessment and consideration of investigation

Sleep apnea?: Poor quality sleep at night due to severe snoring that causes airway obstruction is called sleep apnea. This is one of the most common causes for the day time sleepiness that you are describing. People are often unaware that their snoring is so bad that it is actually stopping them breathing for 20-30 seconds at at time. This makes you partly wake up and prevents you getting REM sleep.