My receiver shuts itself off when I turn the volume up (or randomly mid-movie). Why?

It is protecting itself, and the trigger is one of three things: heat, load, or supply. The pattern of when it happens tells you which.

Heat is the most common in India. A closed cabinet, a long loud session, and the AVR reaches its thermal cutoff and shuts down mid-film. Feel the top of the unit when it happens; if it is uncomfortably hot, you have your answer. AVRs need air above and behind them, and a glass-fronted cabinet with the doors shut is a slow cooker. Open the doors, raise the shelf clearance, add a quiet fan if the cabinet cannot change. Cheap, and it fixes most cases.

Load is next. Two versions. A wiring strand that only shorts at high volume, when the speaker terminals see more current and a stray whisker arcs across; or speakers that are harder to drive than the AVR's rated impedance, so the output stage runs out of current exactly when the film gets loud. Both appear precisely at volume, which is why "it only happens in the action scenes" points here. Check terminations first, it is free: strip cleanly, no stray strands, and if in doubt banana plugs. Then check the speakers' rated impedance against the AVR manual.

Supply is the third. Shutdowns at modest volume, with clean wiring and good airflow, point at either the AVR's own power supply or your mains. Test on another circuit; if the shutdowns follow the AVR, that is authorised service. If they stay with the room, it is the supply, and a stabilizer conversation.

Random mid-movie shutdowns with no volume pattern lean toward heat or supply; shutdowns that track the volume knob lean toward load.

Note the volume level, how long it had been running, and how hot the top was when it happened, and send us those three facts with the model and speaker names. They usually name the cause in one conversation, before anyone unscrews anything.