Certified mad person here; I have experience of seeing psychiatrists and mental health professionals. Please note this experience is UK-specific, so maybe double-check it's still accurate if your MC lives elsewhere.
The psychiatrist would first do a basic assessment using standard tickbox questionnaires, to try and determine what broad group of symptoms (if any) the MC has - for example, mostly anxiety type symptoms, or obsessive type symptoms, or manic type symptoms. These would take about 15 minutes to complete and the MC would either fill them out silently themselves, or the psychiatrist would read the questions out. Here's an example of one of the questionnaires they'd use: https://www.nhs.uk/T...assessment.aspx . This one focusses on mood. The psychiatrist would check the results of this to determine if depression symptoms are present.
The psychiatrist would usually then interview the patient and ask them in their own words how their mood, functionality, anxiety levels and general health is. They will also ask basic questions about physical health to see if these answers are relevant (e.g. how much do you drink, is your diet adequate, do you have a chronic health condition that affects your life etc...?). They do this partially to check whether any mental symptoms could be attributed to physical causes (like, if a patient feels exhausted, tingly in hands and feet, anxious and foggy-headed, and admits they eat like crap, a good doctor might check for a vitamin B12 deficiency).
After about 30 minutes and these questionnaires, the doctor would usually either make an assessment of no diagnosable condition, or go on to more detailed tests for suspected disorders (maybe rescheduling for a second appointment if this could take a while). For example, if obsessive type symptoms are found and is suspected, at this point they'd administer an OCD-specific test called the Yale-Brown Obsessive-Compulsive Scale. I think this is done for other disorders too.
If you don't intend your MC to actually be any diagnosable form of mentally ill, that's fine, and a good psychiatrist would discharge him at this point and say there is nothing technically wrong. If you DO intend your MC to be suffering from some form of actual mental illness, accuracy would be preferred if you can manage it. Those of us with mental health conditions kind of want to hunt down the author and make them eat their own book when we see YET ANOTHER CASE OF OCD represented as characters giggling over being organized and enjoying handwashing (...actual OCD is a million miles away from the way it's shown in the media, and way, way darker and scarier). Representing mental disorders fairly and doing your research is SO important for breaking down the stigma around 'crazy insane people'. I can't stress enough what it big favour it would be to 10,000's of mentally ill folks to see this done accurately.
There are some forms of mania, delusional disorders or depression/suicidal ideation that could make the MC deliberately endanger their life (if mania or delusion, it's usually because they don't fully realize the danger; if depression and suicidality it's probably because they genuinely want to die). But plenty of people do reckless extreme sports or dangerous stunts without having any real mental disorder. They can just have an extroverted temperament and enjoy an adrenalin rush or have a 'live fast, die young' personal philosophy. Your MC could be in either category depending how you write him.