I see you have POTS from your profile! I have unspecificed dysautonomia (the fam POTS belongs to) and what you're describing happens to me everytime I push myself too far. That limit varies day to day but as soon as you start feeling that way I recommend stopping and sitting down or it'll just get unrecoverablly worse as you said. I bought a rechargable neck fan and it's super helpful for managing flare ups like this, I couldn't live without it! Sitting with a fan on you might speed your recovery up Basically, I think it's probably POTS related. Being anywhere near those hot appliances as well as moving around a lot at your job may accidentally be triggering your symptoms. The tingling numbness could be due to blood pooling and/or poor circulation. Hope this helps, please take breaks more often in a cooler location to try and avoid this!