Exactly. I didn’t want to accuse OP of buying cheap tape, but proper electrical tape will be clearly labeled as electrical or electrician’s tape, will have the NEC standard on it, and costs $3-$5 a roll unless you’re buying in bulk.

And even then the minimum is 170 degrees. 3M and a couple other companies certify their vinyl tapes above that, but one that’s barely compliant could still get hot enough in a hot car for the glue to start to soften.

The tape itself has NEC standards regarding when it melts and burns, and is designed primarily to melt unless exposed to really extreme temperatures. There’s usually a rubberized or vinyl part of the tape that can turn it into a sticky mess. Good electrical tape shouldn’t have problems at “normal” temps, but on a hot day in the south/southwest a car can get upwards of 150 degrees F, which is pushing it even for the good stuff.

Humidity also doesn’t help and can cause some glues to break down faster.