MetaTrader 5 is sluggish and your computer fan is loud.
Too many open charts, heavy indicators, or a large journal and logs.
MetaTrader recalculates every indicator on every chart as ticks arrive. The load is therefore roughly the number of charts multiplied by the indicators on them multiplied by the tick rate of the symbols involved, and it rises sharply during volatile sessions when ticks come fastest. A setup that feels fine in a quiet Asian session can struggle at the London open purely because the tick rate has multiplied, with nothing having changed on your side.
The maximum bars setting compounds this, because indicators that recalculate over the whole history do more work when more history is loaded. Log files are a slower-burning version of the same problem: the terminal writes journal and expert logs continuously, and on a machine left running for months these accumulate into a large number of files that make the folder slow to read.
Watch the terminal during an active session rather than a quiet one, since that is when the problem shows. The chart clock should keep up with real time and the interface should respond immediately to a timeframe change. Task Manager on Windows gives the objective measure: the terminal's processor usage should drop noticeably after removing charts or indicators.
Keep only the charts you actively use open, and be deliberate about how many indicators each carries. Set maximum bars to a number that suits your analysis rather than the highest available. If you run several Expert Advisors continuously, a VPS moves that load off the machine you work on, which also protects the automation from your own restarts.
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