O-o , Laptop? Elevate off desk, turn it on, run it elevated (for proper cooling) , run a benchmark, see if it gets hot, monitor your cpu temp with software.
If it crashes, most likely not over heating from being against the wall and blocking the exhausted ambient heat.
Laptops by nature can get really hot, similar to the reasons a Phone can (esp I-phone [IMO]) .
If it doesn't crash , then get some compressed air, and clean out all vents, continue testing, but do some actual tests, I have yet to see any attempts, run the tests and software suggested, post results.