On my machine (MacOS, 2.7 Ghz i7, 16 GB RAM, 750 GB SSD), IntelliJ IDEA performance is quite acceptable. Some students, particularly those running Windows on older machines, have complained of slow compile and test times.
As a first step, if IntelliJ does not load within 10 seconds, the most likely culprit is your virus protection software. Please make sure your virus protection software is not checking the binaries or jars of IntelliJ on startup. The most simple test is to entirely disable virus protection and see if that fixes performance problems. If so, then selectively re-enable protection to avoid IntelliJ impact.
If virus protection is not the issue, you can try one or more of the following, which has worked in the past for other IntelliJ users:
More drastic measures include adding RAM or switching to a solid-state disk.