The 2 big concerns with an e36 328i are cooling system and Nikasil.
The alloy block on the M52 doesn't like being boiled. It warps if its overheated and it can be almost impossible to effectively repair so the engine can end up as a big paperweight. Therefore, the state of the cooling system, rad, water pump, thermostat, etc. are important.
Nikasil was a material used to line the bores of early M52 engines, from introduction in '95 until the liners were updated to Alusil around March '98 production. High levels of sulpher in petrol, combined with lots of cold starts and short runs, can cause a chemical reaction leading to the bore lining being degraded to the point where compression diminishes and impacts on the engine running, cold starting, etc. High levels of oil consumption was a big symptom of the issue.
Back in the day BMW replaced a lot of engines and not all were affected (my first e39 ran until well over 180k before I lost sight of it and still never needed a top up between changes). That's one reason why a lot of early e39's and e36's disappeared fairly early on and why they are relatively scarce now.
A good engine with no cooling issues and no nikasil issue is a very reliable and long lasting engine though. The same was true of the 2.5 engine used in the 323/523 and the 2.0 used in 320/520. They were all part of the m52 engine family, and also used in the e38 7 series.