One of the likely reasons for exhaustion after getting the vax (or getting the actual virus), is that in both cases your body is exposed to the spike protein that binds to ACE2 receptors on your cells. The mRNA "vaccine" causes your body to produce the spike protein.

https://www.salk.edu/news-release/the-novel-coronavirus-spike-protein-plays-additional-key-role-in-illness/

From the above article, is the following quote

..."They showed that the spike protein damaged the cells by binding ACE2. This binding disrupted ACE2’s molecular signaling to mitochondria (organelles that generate energy for cells), causing the mitochondria to become damaged and fragmented."

Mitochondria are the power house of the cell that produces ATP which powers all internal mechanisms of your cells. Damaged mitochondria don't work efficiently. Systemically this would cause cellular energy deficits and that would naturally/ logically lead to exhaustion as your cells could not convert calories to ATP.

The vaccine isn't harmless it makes your body produce the spike protein that will bind on ACE2. Binding on ACE2 with a spike protein disrupts internal cellular processes. It's basically a really bad idea. Not to mention the other vaccine side effects and the significant potential for the vaccine to cause autoimmune disorders or immune system collapse around 6 months to 2 years from getting the injection.

I have family and friends who got the vaccine. I am 95% sure that one extended family member of mine who died suddenly / unexpectedly recently was 2 weeks post getting the vaccine (there were some things said at funeral suggesting he got vaccinated recently, but nobody said specifically). I hope the rest of my family turns out ok from all this as they all got vaccinated ASAP.

Another family member had an unexplained severe nose bleed incident that required an ER visit. It was completely out of the blue and they never had anything like that happen before the vaccine. This was about 1 week after vaccination and they had felt exhausted and a little unwell 4 days prior, then felt ok 2 days prior, then had this nose bleed that wouldn't clot off. Ended up with a balloon in one side of her nose and even after a few days they still had to go in and cauterize the blood vessel. It was as if the blood vessel's wall just disintegrated out of nowhere.

Many whom I know got vaccinated at the very least complained of significant tiredness within the first two weeks of getting the vaccine.