Okay, a hells gate touch mod, description of your batteries are LG HG2 20amp 3000mah, you are running at 35watts. Missing is what atomizer/tank attachment and what resistance of the attachment coil, this measured in Ohm's. Now if the tip of the attachment is getting to hot at 35watts you are not pulling enough airflow to help cool things down. The mod and attachment will get warm if you chain vape, thermal dynamics is a great category of physics, gets to warm set it aside.
The critical part you don't want getting hot are you batteries, as long as they do not get to a temperature you can not touch them, that is danger zone for them, open the case and touch them from time to time, if you can hold your fingers on them for more than 5 to 10 seconds, batteries are still good to go. If they are about 20 to 25 degrees F over room temp set the mod aside and let it cool down to room temp again. Remember some attachments are just naturally hot running units, examples the Aspire Cleito tank and Smok TFV8 naturally run hit if chain vaped. Might look into investing in a second mod/tank set to rotate so you are over cooking one all the time chain vaping.
Sitting on the couch